That's a good buying price. You might get $60 or more on eBay. Consider the manufacturing standards for those games; the stickers peel, actiplaque, the battery doors get lost (no screws back then) for some reason people scratched up the screens, etc.
Surprised anyone at any yard/garage sale or even an antique store (where prices get into the Bifröst Bridge range of unreality) would stick a $30 tag on a plastic 1980's game. Who knows who spoke to whom. But you can play it and enjoy the game and fact you got it for half off, or sell it and get your money back! I'll give you $50 from a PM offer if you want to sell it and it's working.