Prices on Ebay are just like I toss darts......all over the board. I have found some bargains on ebay, some even on GunBroker, but those are extremely rare and go fast when found.
The two things both sites offer...a wide search net across the nation for obscure items. Almost all are over-priced, but when you can't find it anywhere else, they have you by the short and curly.
For example...I just picked up from GB a complete T/C 54 cal White Mountain carbine that had been demilled by sawing off the breech for $160..I say complete...... Lock, trigger, tang Stock, Hardware, Ramrod and the demilled barrel (now 18") with stock sights and underrib. One hell of a deal. Yet complete WMC 54 or 50 cal stock on Ebay, with lock and trigger are listed for over $350..go figure.
It pays to frequent and shop.