What kind of classic car parts if I may ask?
I find ebay almost impossible to use for that. Generally speaking anything OEM by the manufacturer is in far far worse condition than represented or have starting prices something like 10X what they'll go for at the Owners club swap meet if you wait for summer, or catch a classified listing in the club mag.
As example, you'll see things like steering wheel assemblies that look great on the outside but an ebay seller won't tell you the plastic switches inside for the horn rim have turned to confetti. If you contact them they'll play dumb, as if they did not hear all the rattling debris inside when they were photoing the thing. Granted it still a usable part if you have CAD skills, a 3d printer or lathe, and are okay with having to 'fix it again' every few years but..
When it comes to adjacent stuff like brake parts, carb parts, etc, I find half the time they are Chinese knock-offs being sold as OEM for darn near OEM prices. They may look and work fine but often there are subtle things, that master cylinder sure its got a slightly shorter rod, fits works fine, but you can't replicate the original pedal travel exactly etc. Oh and you could have ordered from Rock Auto for 1/3 of what you paid.
I pretty much have given up on Ebay entirely for parts.