Cat teeth extractions/dental work. How expensive, & have you done it?

I've been caring for a very affectionate stray that has HIV and Kidney disease. He has terrible breath, and all of his black teeth are blackened and rotten. He eats, but sometimes he cries out mid bite sometimes (rarely). My vet doesn't do teeth extractions, so I'll have to shop around. Has anyone ever had it done? And how much did it cost you? Or how much was any cat dental work in general? X-rays, exams, etc. vets are really affordable in Japan (which I've been so thankful for), but I've never dealt with a cat dentist. Thank you.