From Anastasia Tsioulcas at Deceptive Cadence:
Long, long ago — say, the late 20th century — labels put releases into three distinct categories. “Front line” releases were new recordings made by current artists, and they fetched the highest price at retail, somewhere around $16 or so for a single CD. “Mid-line” releases were usually reissues, frequently remastered and very lavishly repackaged, whose retail cost was about $10-12 per CD. And “budget” releases were either new recordings made relatively inexpensively by unknown artists (a field the Naxos label dominated), or they were reissues and compilations done on the cheap, often by third-party labels. (These labels were — and often continue — to be based in Europe, where copyright holds for just 50 years, making all sorts of prized treasures among great recordings fair game, even if they weren't technically allowed to be sold in the U.S., where copyright holds longer.) And even as late as last year, new “front-line” digital releases were generally priced at about $10.
More here.