This really only applies to pre-CBS Fenders, and honestly I’ve seen refinished vintage pieces sell for decent money (Kebo’s).
It pretty much applies to all years and all brands across the board.
But don't take my word for it. Look on ebay. A refinished checkerboard binding 4001 recently sold for $1,800. That pretty much half of what he could have gotten for it if it had the original finish. There's a refinished '79 Pbass that sold for $900. That's close to half the going price for an unmolested example. And so on, and so on....
You may have seen some refinished pieces sell for decent money. But they'd have gotten much more decent money if the instrument wasn't refinished.