Agree with everyone above. Kodak stop bath is butt cheap here. And it's fun to use, it starts out very light yellow then turns a color like pee when you've been drinking gatorade, then eventually goes purple and you make more.
I mix the stuff a liter at a time and I'm only on my second liter after running one batch of Xtol out, so I'm guessing based on 1 roll of 120 a week you should have, roughly, a lifetime's supply for your $7 or whatever it costs. I just bought mine when I was buying film and some other supplies so the shipping cost was mitigated. But if you DO pay for shipping, call it $20 for a lifetime supply.