most a bands revenue or income is from touring venues an merchandise, or sign-on bonus and contract renewal bonus'.
if you want to support a band, see them in concert, and buy a shirt or something while youre there.
however buying their album keeps their contract updated, keeps them in the record studio, and basically keeps them employed, however it does not pay their bills.
i knew a band once that got a 100k$ sign on bonus. split 5 ways, after they purchased a Tahoe and trailer to haul equipment. they each got ~12k$. each member spend another ~5K upgrading their equipment, the remainder had to last them the entire time they were on the road for, i wanna say Warped Tour 04 or 05. by the end of the tour, each were near broke. by the time they got in to finalize the record, two had quit the band, and they were dropped soon afterwards.