Spinoff on the BR Bums and Beggars

I sometimes make a quick stop on my way home for drive-time refreshments and it happens to be very populated with beggars. Most are obviously looking for money for whatever habit they have. The odd thing (to me anyway) is that they are always asking for small change. Most of the time they ask for 35 cents of 45 cents. Kinda odd amounts. I've only given in about twice over the years, but I see others give them change often. The second odd thing I've noticed is that anytime they get a handout, they immediately take off around the building, like they're off to get what they need with the change.

What the hell are they getting with that small amount of money? I'm not real in touch with the drug prices these days. Is there some drug that is really that cheap?