A 1000 gallon tank give 666 scf starting at 175 psi, and dropping to 100 psi. If your blast cabinet needs 50 scfm, it will run it for 13 min. . .
Yes, and that's in the 'really big' category I mentioned. Few have room for such a tank, and 13 minutes wouldn't get me very far with abrasive blasting either. 30 minutes would be a starting point, and the long refill time remains a problem. I personally would not be comfortable pressurizing a reject 1000 gal tank to 175 psi year after year.