I've got bum knees, trecking poles are a godsend.
Can't comment on the costco poles, but costco is great about returns when you break stuff
My first pair of trecking poles were a cheap pair that I bent the first time out in less than an hour. Then I got a pair of BD trecking poles and it took me several years to bend them. About 20 miles in Crow Creak I slipped on an off camber patch of mud, managed to save myself with a pole plant but bent it pretty badly. I was able to straighten it out without any cracks or stress marks, though it doesn't quite fully retract now.
I wouldn't go with carbon fiber, they are slightly lighter but they won't bend when over stressed, they'll shatter. Also using them in rocky terrain will nick them up which will lead to them failing.
