The issue here is that you were wearing jeans from the Gap. I blew out a pair of Gap jeans the first week I had them just walking around--and I'm no fatso at 6' tall 170 lbs. Their quality control is just shit. Stop buying things from them. I did.
I know it goes against your budgetary constraints, but pick up a pair of Prana climbing pants from Rock and Snow. They're good guys and the pants will last you a long time. Prana doesn't make my favorite ones anymore, but I have a pair of these
. The cinch strap for the waist strap loosens up on its own, but other than that they're great. You'll be able to use them for years and come in at about the same cost as a C3.