Well, there is really no record for that unless one wants to take the time to look into Intrada releases in recent years that were discontinued because interest didn't remain even a year.
Other than that, only FSM and LLLR have really spoken up. The only "recent" title for LLLR was Elfman's PotA 3CD set, which only sold like 1,500 or the 3,500 announced copies.
EDIT: LLLR's is discontinuing "Green Lantern"; I've not seen a word on how many were pressed of the original announced units. But most of the time we don't get those precise numbers. When we do, I ad them to the www.en.scorepedia.org page for the label.
What about when the labels have clear-out sales at deeply discounted prices?
There were loads of great titles in that MovieScore Media blowout sale going for really knock-down prices a few years ago, presumably because they were for relatively new and unknown composers on smaller genre films.