Sure, Costco AND Wal-mart are known for savings on everyday items like a 36-roll pack of toilet paper and $4 prescriptions. But can you trust a warehouse club or big-box retailer when it comes to your wedding?

Discount retailers have been breaking into the wedding business, offering products at a fraction of the price you'd pay at bridal boutiques or florists. Costco (COST) is turning into a one-stop shop for brides and grooms, carrying everything from engagement rings to honeymoons in Tahiti. In the last year, Wal-Mart (WMT) extended its relationship with Martha Stewart to include a wedding collection complete with invitations, albums and other nuptial-related accessories. Sam's Club (owned by Wal-Mart) now devotes a section of its web site to wedding products, and says it s expanding its selection. Even supermarket chains like Publix, Acme and Albertson s are getting into the business, selling wedding cakes.

All of this comes as many engaged couples are scaling back on their big-budget weddings. This year couples are expected to spend an average of $20,400 on their weddings, down 6.5% from 2008, and a 29% drop from 2007's average of $28,700, according to The Wedding Report, a market research firm.

See what deals you can find at big discounters.

Of course, there are some trade-offs to buying your invites at Wal-Mart or your flowers at Costco. When you go to a printing shop or stationery store, a professional walks you through every step of the invitation process, helping you select paper, ink color, wording and font style. Getting your invitations from Wal-Mart, though, is a solo and more time-consuming effort, says Robyn Bruns, owner of Red Letter Event Planning in Chicago. You need to give yourself a lot of time, and you need patience to do them. I ve had brides start out doing it themselves and [then later give] up, she says.

The good news: Most guests won't be able to tell the difference between invitations from Wal-Mart or specialized ones from a printer. You don't have to sacrifice on quality or style because the options are on trend and well-priced, says Jamie O Donnell, a wedding planner in Orlando, who buys from discount stores for both her higher-end and more budget-minded customers.

SmartMoney decided to go shopping with some wedding planners to find out which offerings are worth buying at discount stores like Costco and Wal-Mart, and where to find the best deal.

Price at printer (for 100 invitations): $800 or more

Price at Wal-Mart (for 120 invitations): $120

Potential savings: 85% or more

For a 100-person wedding, invitations can cost between $800 and $1,000 (or more, depending on paper thickness and printing method). Go the do-it-yourself route and you can pay a fraction of the amount. O Donnell favors Wal-Mart s Martha Stewart collection they re good quality and easy to run through your computer and printer, she says. A set of 40 invitation kits, including response cards, envelopes and ribbon embellishments, costs $22 (three sets come to a still-reasonable $120).

Pickier brides can go to Costco, which sells invitations through eInvite.com, a web site that customizes and prints invites. Costco members save 25% to 30% off regular eInvite prices. While more expensive than Wal-Mart s -- on the lower end, 100 invitations would run around $140 and response cards, which are sold separately, cost about $60 the selection is wider and brides can order samples before committing to the purchase.

Price for six bouquets at the florist: $375 and higher

Price for bulk flowers at Sam's Club: $88

Potential savings: 75% or more

Barbara Cohen, a floral decorator in Monsey, N.Y., says she charges $125 to $150 for an all-rose bridal bouquet, and $50 to $75 for a bridesmaid bouquet (prices vary depending on type of flower, region and season). Buy a bridal bouquet and five bridesmaid bouquets and you re paying a minimum of $375. Again, do-it-yourselfers will save even more. A package of 125 pink roses at Sam s Club costs $88 (shipping included) can make at least six bouquets. Keep in mind that you ll need someone with a green thumb to help you turn those loose stems into a showpiece, says Bruns.

Don t trust your bouquet-making skills? A 20-piece red rose collection from Costco which includes a bridal bouquet, two bridesmaid bouquets, three centerpieces, two corsages and four boutonnieres costs $230.

Typical price: $400 and higher

Price at Publix supermarket: $300

Potential savings: 25% or more

Instead of a traditional tiered cake for a client s September wedding, Sacramento event planner Celeste Armendariz plans to pick up five cheesecakes from Sam s Club. Grand total: $100. A wedding cake from a local caterer would cost her around $400, she says. And that may be on the cheap side: Professional wedding cakes which are priced per slice can reach four-digits depending on filling, decoration, size and even, where you live.

If cheesecake isn't your taste, head to the supermarket. Publix sells a traditional wedding cake that feeds 100 people for about $300. And they're customizable: Customers can choose from various styles, fillings and toppings, and can even bring photos from magazines of cakes they d like recreated.

Price of men s white gold wedding band at Kay Jewelers: $400

Price at Costco: $157

Potential savings: 60%

The only real difference between a gold wedding band from your local jeweler and one from Costco is cost. That s because individual jewelers charge bigger markups than warehouse clubs, which can afford to buy in bulk from manufacturers and take smaller margins, says Jerry Ehrenwald, CEO of the International Gemological Institute.

Costco carries a 14-karat 6mm white gold band for men for $157. A similar ring from Kay Jewelers is $400, and $185 at Wal-Mart.

Price of gift boxes at WeddingFavorites.com: $81

Price at Wal-Mart: $52

Potential savings: 35%

Wal-Mart s "Celebration Centers" carry a great selection of favor items, says O Donnell. Martha Stewart s line of favor boxes, for instance, sells for $10.46. Five sets (for 100 guests) will run you about $52. Comparable cube boxes from WeddingFavorites.com are about 35% more.

Costco and Sam s Club are the place to buy in bulk and perfect if you plan to send your guests home with a homemade candy gift bag. Lisa Green, owner of Anderson Green Events in New York, bought $100 worth of candy and mini chocolate bars from Costco for a wedding last year. Had she gone to a supermarket or drugstore, she says, the same amount would have cost close to $250.