Any advice on Trading-in Iphone 4/Bad Home Button?

Like many others my iPhone 4's home button isn't very responsive. I can't figure out if the problem is due to buildup behind the button or the cable connection as one corner of the button works causing me to think its dirty but recalibrating it had it working a little bit better it seemed. I tried the alcohol cleaning, toothpick, etc... and tomorrow I'm getting compressed air & connector cleaning spray/fluid to try to clean it. In the end I'm planning on getting the iPhone 5 but I want to trade it in for credit. Apple & AT&T are the only places I can think to trade it in and while Apple seems to offer more (AT&T only $158 for fully working) I would be without a phone for a while. According to the AT&T the company removes around $100 for something not functioning so I want to try to either get the button working better or find somewhere else to trade it in that offers more money. I would go to an Apple retail store in the event they do trade-ins in-store but there aren't any anywhere nearby. Any advice?