I've got other ideas but let me start with this one. Engaged couples (and young marrieds who have not been exposed to this) need to see in black and white just what items married people spend money on. I am not making any judgements about priorities in the list that follows; the purpose is strictly to delineate areas that can/may be spent on when married. These couples have surely seen these items in their parents' homes or in other people's homes, but I don't think it registers with them that they, too, will have to possibly spend to buy these items, now and in the future, and just how much everything costs.
HOUSING: rental costs, security deposits, mortgage payments, down payments, real estate taxes, closing costs, moving costs, monthly utility charges (gas, electric, phone etc.), air conditioners, painting, routine maintenance costs, landscaping/yard maintenance costs, apartment/home owner's insurance costs, unexpected repair/replacement costs.
HOUSEHOLD FURNISHINGS: floor coverings, lighting fixtures, window coverings, major appliances, minor appliances (mixers, blenders, toasters etc.), furniture, bedroom and bathroom linens, mattresses, baby furniture (cribs, high chairs, carriages etc.), kitchen and dining room linens (dish towels, aprons,pot holders, tablecloths etc.), kitchen cookware and utensils, silverware and dishes, trivets, bake ware, decorative ware (mirrors, pictures, crystal and silver and china items, vases etc.), storage items, home technology (phone systems, cell phones, clocks, shabbos clocks, music players, computers, televisions and radios etc.).
HOUSEHOLD MAINTENANCE AND REPAIR: basic tools (hammer, screw driver etc.), basic fix-it supplies (nails, screws, duct tape etc.), tape measure, household cleansers (including dish washing supplies such as sponges and soaps etc.), brooms, mops, dust pans, light bulbs, bucket, laundry detergent and supplies, laundry baskets, laundry hampers, vacuum cleaner, de-icing agents for walkways and driveways, shovel, cloths, sponges, scrubbers, steel wool pads, squeegees, disinfectants, bathroom deodorizer sprays, carpeting cleaning supplies, stain removers, rubber gloves, cost of repair or service people, cost of cleaning help.
HOUSEHOLD HEALTH AND GROOMING ITEMS: health insurance, prescription drugs, OTC medications, vitamins, first aid supplies (thermometers, bandaids, gauze tape etc.), dental/mouth care items (toothpaste, toothbrushes, mouth wash, chap sticks etc.), hair-related items (brushes and combs, shampoos, conditioners, shower caps, bobby pins etc.), bathing/washing related items (soap, body wash, lotions, deodorants, sponges etc.), nail/hand/foot care items (scissors, clippers, emery boards, polish, lotion etc.), feminine hygiene items, exercise equipment (weights, treadmills etc.), general items such as Q-tips and cotton balls and cotton pads, makeup, perfumes, aftershave lotions, home personal care items (irons, hair dryers, shavers etc.).
OUT OF HOUSE HEALTH AND GROOMING ITEMS: dry cleaning, shoe repair, doctor visits, clinic/hospital care, dental care (check ups, fillings, braces etc.), eye/vision care (check ups, glasses, sun glasses,contacts etc.), diapers and formula, hair care (cuts, styling, sheitle combouts etc.), gym memberships.
TRANSPORTATION COSTS: public transportation costs, car purchasing, car leasing, car insurance, gas, routine maintenance costs (oil changes, tune ups, new tires, brake work etc.), state costs for licensing and registration, state inspection charges, leisure time costs (air and train tickets etc.) school transportation costs, parking charges, unexpected costs (parking tickets, accidents etc.).
READING MATERIAL: general secular books, seforim, magazines, journals, newspapers, education-related reading material. And then there is Internet connection costs.
RITUAL ITEMS AND RELIGIOUS OBSERVANCE COSTS: lachter, bechers, chalah covers, boards and knives, chanukah menorahs and supplies (oils, wicks, candles etc.), kittlach, talisim, kipot, talis battel, tzitzis, tefillin and tefillin battel, esrog box, honey holders, lulav and esrog, sukkah, schach, matzas, seder plate, matza cover, passover dishes and foods, shalach monos containers and contents, Shabbos urn, blech, monthly mikveh charges (or more often if a man also uses the mikveh), shul charges (seats for yom tov, yearly membership fees etc.), tzedaka donations.
WEARING APPAREL: dresses, skirts, blouses, suits, shirts, t-shirts, sweaters, sweatshirts, undergarments, socks and hose, pajamas and nightgowns, robes, pants, belts, swimwear, jackets, coats, gloves, scarves, mufflers, purses, wallets, briefcases, shoes, slippers, boots, sneakers, hats--both male and female, tichlach, sheitlach, accessories (includes jewelry--both real and costume, tie pins, cufflinks, hair ornaments etc.), neckties, special occasion gowns, multi-size wardrobes (for when you've been married a little while). Note: for when there are children in the home, you can add in most of the list for them as well, only you'll be replacing these items each time a child grows.
DRINKS: coffee, tea bags, bottled water, sodas, juices (fresh and bottled), milk, powdered drink mixes, wine, grape juice, hard liquor, beer.
PAPER/DISPOSABLE GOODS: toilet paper, boxed tissues, paper towels, table napkins (Shabbos and everyday), paper/plastic plates, paper/plastic drinking cups (hot cups, cold cups, bathroom cups etc.), table covers, plastic silverware, aluminum pans of all sizes and dimensions, aluminum foil--regular, extra long and shabbos pre-cut, plastic wrap, waxed paper, garbage bags (kitchen size, trash size, recycling etc.), plastic food storage bags--multitude of sizes and types, cupcake liners, special occasion disposables (birthdays etc.).
PERSONAL STATIONERY NEEDS: computer printer paper, computer ink cartridges, personalized stationery, greeting cards, thank you notes, staples and a stapler, post it notes, paper clips, scotch tape, rubber bands, pens and pencils, notebooks, folders, wrapping paper.
ELECTRICAL/BATTERY-OPERATED ITEMS: Note: a few items are duplicated or covered in other categories. Extension cords, surge protectors, night lights, flashlights, fans, air conditioners, humidifiers, dehumidifiers, timers, answering machines, PDAs, Blackberries, cameras of all types (added expense for film or accessories), cell phones, computer games, kitchen and bathroom appliances (the sky's the limit here), lawnmowers, snow blowers, etc., etc., etc.
GIFTS AND ENTERTAINMENT: CDs, cable service, live performance tickets, restaurant meals , meals served to guest in your home, going to the movies, tickets for sports events, games, toys, vacations, date nights, baby sitting costs, gifts to those outside of your family (birthdays, anniversaries, engagements, weddings, bar mitzvahs, brisim, baby births, etc.) as well as gifts to each other. And yes, let's count summer camp in this category.
LIFE EVENTS: engagements, weddings, sheva brochos, brisim, upsherin, bar mitzvahs, bas mitzvahs, kiddushim (lots of reasons to have to/want to make these), anniversaries, birthdays, holiday observances, graduations.
EDUCATION: pre-school tuition, elementary school tuition, high school tuition, post-high school yeshiva/seminary tuition, college tuition, graduate school tuition, specialized certificates and/or training courses, books and assorted school supplies, school uniforms, mandatory yeshiva dinners, chanukah "gifts" to teachers, extra transportation costs for schools not local, dormitory and associated living costs.
FINANCIAL EXPENDITURES: student loan repayment, credit card balance payments, checking account overdrafts, financial institution charges for basic services, IRAs, 401Ks, other savings vehicles, emergency expenditure account (a rainy day account, and it always rains), paying taxes.
WORK RELATED EXPENSES: items that you have in other categories but that you will need more of because they are required for your job, special uniforms, required electronic equipment, added transportation costs, day care expenses for young children still at home.
FOOD: I'm not going to list every single food item that someone can and does buy for their home, but there are some categories that are relevant. Meat, poultry, fish, dairy products, spices, sweeteners, condiments, fruits, vegetables, grains, drink items (see separate category above), canned goods, packaged products, baked goods, frozen food, fresh food, snack items, bread products, etc., etc. etc.
The list above is not exhaustive, although I'm getting exhausted just thinking about all those items. But if engaged couples were faced with such a list, they might have a more realistic view of where they may have to put their money when married. And if they were further told even the average prices for the things on this list you might be able to lead them from shock to the idea that you can't always have everything you want all at the same time, and that budgeting is a necessity.