DC's Archive Editions are among it's prestige items. As a result, they carry a higher price tag than usual, ~$49.95 U.S. For many fans, this precise can be prohibitive. Ergo, it is worthwhile to consider other options of getting them at a better price.
EBAY
The web services at eBay.com allow one to bid on Archive editions. Prices on these editions vary from full price to significant discounts, as low as $10 for early releases. One can find DC Archive offerings by searching the Comics section for either Archive or Archives. At any given point, there are generally 70-100 different Archive selection available so competition keeps prices regulatted. The limitation is that one has to bid, then one has to win and then one has to wait. I have obtained about one third of my Archives this way but it is often simpler just to buy the books outright.
RETAIL OUTLETS (Comics specialty)
The largest comics dealer specializing in discount Archives is Silver Age Comics.com. This source offers all Archives editions for a flat $35 plus S&H. You can contact Gus, manager of SAC, by e-mail to discuss Archive purchases.
RETAIL OUTLETS (General)
The largest general book outlets are Barnes & Noble.com and Amazom.com. Availability is highly variable at these sources and prices range from large (40-50%) discounts to none at all. However, these sites and some of the smaller sources are frequently running discount programs that allow you to get better prices beyond the web offerings. A clearing house for "web coupons" can be found at Amazing Bargains.com. If you suffer from being Canadian, a similar venue exists at Chapters.com.
The upshot of this page is that while DC Archives are premium products, a little intelligent comparison shopping will get you these editions at a price lower than a potential Trade Paperback. Efforts should then be dedicated to using this info to complete you collection of DC Archive editions (and of course, press for new ones!).