Farrier rasp question?

I’ve got a buddy looking to unload a a bunch of old used farrier rasps. Any idea on the market value for these? Figure they’ll have resale value to knife makers above scrap value.

First of all they need not to be case hardened, a lot of the new ones are and are worthless to a knifemaker. I use them a lot and test them by bringing them up to temp and water quench them. I put them in a vise and see if the tail breaks or bends, if they bend they go in the trash.
I buy old ones from Texas Farrier Supply in Mansfield Tx. for $5.00 each. All I've ever bought from them were usable, I recently had a farrier that my brother uses give me 10, all were worthless.

Forgot to mention, I only bring the tail up to temp in a gas forge.

If they will work, I then anneal them and turn a five buck rasp into 5 or 6 hundred bucks.