Look again. The highest sold price for a 3"/1.9 Oscillo-Raptar now visible on eBay is $202. Still pretty absurd.
The lens, as you stated, is made for oscilloscope cameras. It is designed to image on the inner surface of a cathode ray tube on 3 1/4 x 4 1/4 film. In other words, it is designed to perform best close up. Yours is intended to work with a 'scope whose screen is 1.1 times the film's size,
People have tried to use these beasties as taking lenses on 4x5 cameras at distance. The consensus is that they're not worth bothering with. They're also not very good as macro lenses.
Oscillo-Raptars' main competitors in the US are Oscillo-Paragon lenses made by Ilex. 80/1.3 Oscillo-Paragons have brought silly money.
I don't know why people pay much for them. They're poor lenses and generally useless. Against this, some are fast and there seems to be a fast pig's ear cult.
I've bought 'scope lenses, sometimes even 'scope cameras complete, for their shutters. I have a very good Ilex Universal #3 that held an Oscillo-Paragon. Against that, I have a busted Alphax #3 with its 75/1.9 Oscillo-Raptar (marked 0.5x) holding my desk down and gathering dust.