Gauntlet 2 - $400 - $500
Punchout - $400 - $500
Tutankam - $500 * Haven't seen this game come up for sale too often in Seattle. Would like to get one.
Mario Bros widebody - $500 - $600
Astrofighter - $250
Depends on where you're buying 'em too. Not sure what the market's like in Illinois but those are some decent titles.
Obviously depending on condition.
Punch Out!! is pretty much a $500 game complete. You might find one in excellent shape for more, but that is the ball park.