I noticed the price spike as well. I had the opportunity to buy the entire catalog back in the 1970s and 1980s when they were being produced, and at discount in the 1980s when they were being remaindered at the Tower Records outlet in New York. I bought a few that interested me, gave some away, and sold some on eBay in the $20 - $30 range. The ones I kept still have a Tower $4.99 AS-IS price tag on the back.
When B-C was still on lower Broadway in Manhattan, I visited and got their nice tour of the duplication room. I still believe it's unfortunate Dolby B was used, as it limited the customer base. and was not really necessary with the high-output low-noise tape B-C used for duplication.
In the end, the tapes sounded good, but not that good, at least compared to cassettes and vinyl available at the time.
Does anyone have a copy of the quantities list B-C issued towards the end? Would greatly appreciate it, and (with permission) would post it to the reeltoreel yahoo discussion group.