I see no problem in paying the fees.
As has been said, Paypal is a BUSINESS, and the purpose of a business is to make money.
By using the proper process, you gain protection as a buyer. It’s not rocket science is it:
Sending (frequently in the case of bike bits) significant sums of money for something you haven’t seen, to someone you don’t know, who may or may not be a long way away, where you don’t have the same consumer rights as paying retail.
Way I see it, you pay the fees for the protection, if you make the decision to take the risk, you have no right to complain because you knowingly cut yourself out of the protection loop.