Personally, I would never pay a fee to try on clothing (Especially go-commando bike shorts!), nor would I ever try them on in the store, for that matter. I figure I just buy the size that I know fits!

I would pay a fee for a bike fitting, as long as it was refunded as part of the purchase price of the bike that I then bought. However, if the "fitting" consisted of a quick approximation of my seat height so that I could test ride, then no, I would not pay for that.