I've seen them as high as 24 dollars each.. .. lately i've been using the ones at Harbor Freight for like $8.95 if i remember right....seem to be decent, at times they have them n sale for like #3.95
I think the replacement blades are the money maker in this particular tool realm. Not a lot of profit in the tool itself, but the bits/blades, etc.? Yes.
As @JLawrence08648 said, buying in quantity from Amazon is the best value. I got /www.amazon.com/Oscillating-Diamond-Ohuhu-Universal-Concrete/dp/B07RYT3C28/ref=mp_s_a_1_3?dchild=1&keywords=oscillating%2Btool%2Bblades%2Bdiamond&qid=1621248225&sr=8-3&th=1&psc=1']this one>[/URL] and have been pleased with the durability. The 7 pc version is diamond/carbide in case you are working with tile.