I picked up some Center's yesterday(Sunday) at a gunshow for $5/apiece. They are pretty good shape, finish is slightly worn. Black followers, bodies marked 04/92. It was at a table with a giant "lets make a deal" sign on it. They had em for $10 ea. or 10/$100 but took $5 for em. They had some British steel mags here locally for $10ea., did not last long I bought several they only had probably 14 or so in a small wooden box. There was a another fellow there yesterday with straight 20 rnder Colts for $10 also, finish was gone, but appeared they would function just fine.
Other than normal people asking $20, $25 and $30 for 30 rnders, granted they were sealed in bags.
ETA: The 30 round steel mags from Taiwan are pretty good also, and are usually $10-$12. I put some green followers in mine are they so far have run flawlessly.