I don't handle my geckos except on occasion when I need to move them. I am sure they can tolerate amounts of handling and I bet that varies between individuals. I would simply look for signs of them being stressed such as really trying to avoid being picked up, not eating, loss of tail size, loss of weight, etc. That would probably tell you more than anything about whether they are stressed about it or not.
I believe there are a few W. Banded breeders here that can answer the price question...