eBay is doing nothing to lock competition out of the online auction market. Buy a domain name, go do some heads down software development for a few months and start advertising. Go ahead and lowball the **************** out of eBay's fee structure. You could be the one to take some market share.
eBay's pricing model is not opportunistic. Premium? perhaps, but so is any smart business who is among the best at what they do.
And their exclusive use of Paypal whether they own it or not is not monopolistic either. I believe if the buyer and seller agree to use cash, a MO, personal check or credit card eBay does not prevent these methods of payment. Sorry, but again smart businesses have vertical service channels