I work at a mom/pop game store.
We have to use a distributor, and pay around $18 for $19.99 games, $26 for $29.99 games $43 for $49.99 games. It sucks because we don't get games until the day after release. If I told you what we pay for systems, you probably wouldn't believe me. I'll just say it's often cheaper to buy from Walmart than our distributors.
Our trade in is usually around half of what we'll resell the games for. Used $49.99 games are $34.99 (you'd get $20 trade in, maybe $25 if really new title), $39.99 new sell for $29.99 used (you'd get $17), $29.99 new for $19.99 used(you'd get $12) and $19.99 new sells for $9.99-$12.99 depending on title (you'd get $5-$7)
I really don't get why people pay what EB charges for used games. For a difference of $2-$5, I'd prefer to have it new. It irks me when people complain about our prices, it's like, have you never been to the mall?
edit: and don't get me started on paying full price for opened games....