I often look on ebay for folk LPs (occasionally CDS.) Yes, some of the obscure folk Lps are expensive. Like you Janet, I never seem to find the obscure folk Lps in 2nd hand shops, library sales, etc. either.
I was looking on ebay just the other day and there was some obscure folk LP (can't recall the artist/or name of LP right now) but it was for sale for over $200.00 for this one obscure folk LP.) All I can say is "Wow" to sell an LP (starting price) for over $200.00!!
Even ones selling for over $35.00 are beyond my means.

Once in awhile I will get lucky and find a good obscure one for under $20.00 and win it! I'm not interested in every obscure folk album I see but sometimes do find ones that interest me even though I am not familiar with that artist/group.
Found Lps by obscure American female folk singer, Dayle Stanley a few years ago on Ebay and bought them at a decent price. Dayle Stanley was a female folk singer out of the Boston area I believe and she had only two albums out in the 1960's. Hard to find.