I previously told you about weeks of misery from cat ear mites being gone in 24 hours. That was true.
Tommy, a small tiger-looking cat who conned me into taking him in, here in Saipan (my original four cats came with me from Japan), had been suffering for weeks from what was obviously ear mites according to my knowledge. The first squirt of "baby oil", consisting of mineral oil and "olive oil essence" with a very minimal odor, stopped the severely lowered ear position, head shaking, and scratching very quickly.
Three or four days later, those signs starting popping up again, slightly, so I gave one more squirt in each ear. Again, very helpful. Then five or six days later, a lower level of those same signs, so I just gave one squirt in each ear.
I think this is the same treatment a vet might charge $50 for. Depending on the severity of the infestation and your cat's overall health, diet, and freedom to exercise and get sunshine, you might need to treat with mineral oil more than once, up to perhaps five or six times, to get complete resolution.
I took Tommy's brother, Toby, to the vet several weeks ago for the same condition. Although I avoided examining the bill for details ( "anger management" ), I suspect I paid $40 to $60 for a squirt of mineral oil in each ear.
It's not a magic cure, but the best thing I have found for ear mites so far.