They oughtn’t to be THAT costly — I’ve seen replacement units advertised on eBay for a tenth of that — but maybe some of the newest designs are.
It was good for smog-laden areas that humanity controlled the tailpipe and other emissions. Carbon dioxide wasn’t hurting anything, but other combustion emissions were. Likewise coal burning is very clean today, as it should be as soon as it is possible. Maybe there should have been a way to give a waiver to vehicles operated solely in open country, where inversions do not threaten, but we have what we have. It does give us a noticeably clean America, which stands as a silent reproach to dirty, dirty countries like China.
They tell me the “manivert” is cracked. I had to look it up - it’s a combination manifold and inverter. Anyway, I think I can buy the part for around $300, and am going to try and talk my son-in-law into helping me swap it out. We’re going to go underneath & take a look tomorrow to see if it’s doable. (Sometimes the way they design things so as you can’t get at it).