I've noticed a few more that are likely rare or at least uncommon.
Elebits, Skygunner, and Cho ren sha68k original soundtrack.
looking at JP sites there's sometimes a few copies of the Elebits album, it's typically priced around 10,000 to 25,000 yen
https://page.auctions.yahoo.co.jp/jp/auction/g394171505
I've never seen or been able to find the Skygunner Soundtrack since it went out of print.
Specifically the first version of 68k it's only in four collections on this database, the complete edition seems to be more common.
https://www.suruga-ya.jp/product/detail/186121154
Also this one: Xardion
https://page.auctions.yahoo.co.jp/jp/auction/f424631103
This is the only copy I can find for sale right now.