I think weathering is in some ways like customizing a car it can “limit the market” for your vehicle ( or train in this case) to someone of similar preference for what was done. I guess I’m a bit of a screwball in that I actually prefer weathering (especially in the brass steam loco market) when I buy used locos and rolling stock, if it is well done I don’t mind paying a bit more than an untouched example.
Orson Roy put it quite well.
As a “runner” I prefer to do my own weathering and will not buy weathered equipment. I’m rather picky up weathering cars, concentrating mainly on the trucks, couplers, and underframe. I’ll “heavy weather” just a few cars.
I made one exception on Ebay this year for a practical reason. I bought a heavily weathered Athearn FP45 that “mechanically” was in new condition. This seller had gone way OVERBOARD and made this engine look like it was washed in motor oil! I winded up being the only bidder! Anyway, since I intended on repainting an FP45 in the Blue EMD “demo” scheme used on an SDP40f that EMD got from Amtrak, I didn’t care what the body looked like as long as it was intact.
Time for the old 91% alcohol bath!