I would not count myself as a professional bike mechanic, but I do know a lot about bikes. With that said, the shop I frequent never has charged me a ‘supply fee’. However, if they did, it could already be incorporated into their existing charges and it just isn’t so explicit. Therefore, a $15 derailleur adjustment could actually be $12.50 for them, but they charge like $2.50 for blah. Thus accounting for any variables and the customer doesn’t know about said supply fee.
Unless this fee is a ridiculous percentage of the total shop bill, then you have a couple of options...
1) Go to another shop and tell that one to stuff it.
2) Pay the fee and well, you get the rest.
3) Learn to fix your own bike and stop paying supply fees and LBS markup.
While I think it is great to give back to the LBS, there is about a 5-20$ markup when I compared things to online retailers. Lastly, I would say this ‘supply fee’ falls under a course I took in college called Managerial Accounting. Basically, a LBS has fixed costs, sunk costs, variable costs and overhead. The variable and overhead costs they have a hard time accounting for (lube usage, etc). So they have to account for this unknown by imposing said ‘supply fee’.
I got an idea though, who votes me as swamp bike mechanic? I charge very low fees and you get to see my beautiful face??? Huh Huh?