AtomSmasher, They sell the PS2 system for $100 and then they sell the extra controller and memory card for $19.99 each so it is like they are making a $40 dollar profit off of each ps2 system traded in this way.
Fair enough, but $100 for a ps2 with memory card and controller is still a better deal then you'll get elsewhere. A quick check at ebay and that is commonly going for around $75, you might get lucky and sell it for $100, but from what I saw most don't.
EB Games and Gamestop are businesses, of course they are going to make a profit, but they are trying to move the ps3's so they are giving a much better deal then they usually do. Also, you can get used kingdom hearts for free when you buy a used ps2 from them, which they normally sell for $17, which lowers their profit margin to $23.
Considering they usually make 100% profit of off used items (as Alan mentioned and as I said you normally get $50 credit for a ps2) this is not a bad deal and its definately not a trick or a scam. If you want a ps3, then this is probably your best route.
edit*typo
There are three problems with that logic though.
#1 You think people wanting to get a ps3 want to get rid of their ps2.
Imho this isn't the case and it's a dumb move anyway. The ps2 has about a year left in it with actual good games and that ps3 backwards compatability... well it kinda sucks, much like the 360 bc.
#2 You think the average person actually thinks something is worth less because it's old. Mind you I think they are insaine, but most people think their 3 year old computer is worth 1000 bucks. Most people also think a ps2 is worth whatever they paid for it originally, when it isn't.
#3 You think people are never going to want their ps2 back so you don't account that into the figures. When the ps3 flops people will be flocking back to the ps2 for a while, much like when the virtual boy took a nose dive and gameboy sales went up. Actually the ps2 (not 3) was the best selling console of the holiday season, due to it's reduced price and the availability of new titles.
And regardless of this, you missed the whole point. You aren't getting a deal because you aren't saving any money and more importantly they aren't losing any money. They sell the ps2 for 100 bucks and they are giving you 100 bucks off. Just because they only give you 50 for the thing when you do a trade in doesn't mean that is what it is worth to them.