Sorry, but there is a serious flaw in your logic.
Used games had to be bought first to become used.
Also, the fact is many gamers who buy used games would not have bought the game at full price to begin with.
Lastly, the draw of the used games can lure buyers into the new game sections, which can lead to purchases of new games.
Saying they don't see a dime from used game sales is a very narrow view of the market.
I'm sorry, but I can't agree.
While we both agree that the "initial batch" is obviously purchased first, Gamestop sells their used copies (usually at 50+% percent profit) at only $5-$10 less, of which the developers see not a dime. To say that gamers "would not have bought them at full price" when they're only saving $5 is a stretch. Make no mistake - we're making the middleman rich without rewarding the creator.
DLC has been bandied about as well, but it has to be understood that DLC as we're seeing it now is largely an attempt to make up for revenue lost to the Gamestop upscale-pawnshop machine. The best example might be Mass Effect 2's Cerberus Network card, which allows free content to first-time purchasers, but it's not unique. Lego Rock Band and other titles are using similar tactics to cut down on sales "lost" in the EB/Gamestop/7-11 markets.
Publishers are not going to take this lost revenue lying down. Monthly subscriptions are being talked about (the Call of Duty franchise), "free" DLC is being offered with new purchases, pay-to-play mini-games (the Battlefield 1943 experiment) are being discussed, and other experiments are just the beginning. Obviously part of this is corporate greed, but their sense of entitlement is being fueled daily by pirating and the oversaturation of the market with "used" sales.
Comparisons with used DVD or speaker sales is simply an apples to oranges comparison. EB/Gamestop is easily one of, if not THE premiere merchant in the public eye for game sales. Well over half of their sales each year are from used games. If there is a brick and mortar commercial analog for speakers or DVDs with the same market share, I do not know of it.
I say these things not with disrespect for the consumer or for any of you (us). We're all gamers who agree that $60 is an awful lot of money for what is often 5 - 10 hours of play time. On the same token, we're all connoisseurs of a medium in its infancy that deserves to see its pioneers and master craftsmen rewarded.
No malice intended and no disrespect meant. It's not popular to take the side of the distributors, but I think it's fair to look at their side of the coin as well.