I bought a 16 oz. bottle of Photo-Flo 200 for $8 USD. I use about 4 drops per 500ml of chemical. That's like 1/16th of a teaspoon (Actually, it's less). That's 16 (to make 1 teaspoon) *6 (to make one ounce) *16 (to make one bottle). That works out to 1,536 spools of 120 film, or 6,826 sheets of 4x5 film. Calculating the final cost per sheet returns a value of.... $0.001 per sheet. That's got to be the definition of a false economy if I ever heard one.
Using C41 stabilizer on B&W in place of photoflo is like using Mobil 1 Full Synthetic 20W-50 on your garden gate-- sure it'll work, but........