I agree that some of the prices on fee-bay are crazy, but sometimes you can find a "buy it now" locomotive at a fair price. What I worry about most is those items that are second hand (maybe even third hand), that some are fairly old and who knows how they have been stored? In the attic? a damp basement? storage unit? I always plan on older locomotives needing taken apart and cleaned, that's just part of the fun right? But at some point depending on how they were stored, parts can become brittle or in need of older parts that can be hard to find. As far as freight cars, if the price is reasonable I'm ok with that. In fact some cheap rolling stock that I have purchased has came with good couplers and metal wheels all ready installed.
Ralph