The reason for the rarity of Brown Bag packages is partly because they're production elements rather than production music. The packages and their updates were extremely expensive when originally released and only major stations could afford a copy. We're talking several thousand dollars/pounds and Brown Bag and others including JR Nelson, could justify charging as much as the market was very different in the late 80s/90s. There was no easy way for the cuts to be shared and buying them was the only option if you wanted high quality sounds.
The packages remain of value, both financially and as usable items. I don't agree with having to pay for vintage material for personal collections and it's also unethical for copyright matters. I posted the full Starfire package from 1985 on here last year and I had to pay to acquire it.
Production elements are often seen in the same way as radio jingles, a totally different kind of collector than someone who likes library music and it's a bit of a closed shop with very few collectors willing to 'trade' as they often had a pay to add them to their collection. We're not talking small amounts, I've paid north of £1000 for jingle and production elements.
Luckily for most of us, collecting library music is much easier. So, personally, I'm happy to post links to a selection of my music library and share with the generous people on the forum however, I'm unable to share certain production elements with the world at large.