Eh, not really. Play N Trade locations are franchised, so every location is more or less independent of the others. Prices for games are entered into the system from the company, but a franchise owner can alter prices as they see fit. This is probably meant to correct errors (Overpricing on certain titles, underpricing on others) and to lower prices for items that aren't selling, but some owners do indeed mark up game prices to ridiculous levels.

At the one I go to the most, most NES games are $3-$5. Sports games, with a few exceptions, are $1. The staples of the NES: Metroid, Mario, Zelda, etc... cost more than the regular games, but they're certainly not $30. Most SNES games are $5, with the better titles selling for more. But the prices aren't too bad, normally. Other consoles follow the same sort of pricing structure, but the more recent-gen items are more expensive, for obvious reasons-- they probably sell a lot more than the NES or Saturn stuff. Gamecube stuff in particular is fairly high at the Cape store. Ikaruga is $40, and I picked up my copy for $20 at Gamestop (Not the best example, though-- Ikaruga's not exactly a common game).

I've been to Play N Trade stores that mark up old stuff to insane levels, worse than a clueless CL listing or a bad flea market dealer. The one I went to upstate had common NES games like Xevious, Astyanax and City Connection marked up to $8. Oddly enough, I did find two great finds at that store: A CIB Kolibri for the 32X, and a loose cart of Mr. Do! for the Game Boy.