Not to mention the fact that changing mounts and modifying lenses requires machine work, which is very expensive (unless you do it yourself)
and completely swamps the cost of the lens. Say you spend several hundred dollars at the local machine shop (assuming you have one, and it can make things like lens mounts...) to save thirty dollars on a lens to go on a camera that, whether you like it or not, is obsolete and nearly worthless.

Top quality, professional grade bodies and glass have never been a better bargain for those who like to use them. I'm using equipment I never could have justified buying 25 years ago, and it cost peanuts - some of it (Nice clean Nikkormat FtN with a 50/2) was free, some so cheap as to be nearly free - a very clean Pentax H1a with lens for $15.

What do you want here?