That link to the ebay camera....that is not unusual at all for the Xenotar lenses, which had known coating issues. Most of what is in those photos is reflections from trees. I had one of those cameras that had much, much worse coating issues on the lens, and I put a hood on it as well as a yellow filter to help w/ the contrast. Honestly, I saw absolutely no difference from the photos from it and the one I had many years ago w/ a pristine Xenotar lens.
On your camera w/ the big scratch, just fill in that scratch w/ a marker pen or black paint (wiped off quickly to leave the stuff only in the scratch itself). Put a hood on it and I guarantee yoyu will be very happy w/ the results. Shoot, I have a Leica R Elmarit lens for sale on the classifieds here that had coating damage on the rear element from previous fungus removal, and shots from it look identical to photos from other Elmarits I have owned. You really have to mess up a lens to impact the IQ, unless we're talking about haze or fungus. Those will certainly impact the images.
A camera w/ scratched optics will undoubtedly bring less money than one w/ a pristine lens (photographers will buy it, posers or collectors will snub it), but you figure on buying it cheap, so you sell it cheap. It equals out.