I am a big fan of various subgenres of prog-rock.
Some of the best prog of the 70's (and current era for that matter) came from Italy. Better known bands are PFM, Banco, Le Orme, Arti e Mistieri, Area and a few others. But Italy was also known to have quite a few bands that were "one-and-done". Released one album, then disappeared into who knows where.
Some of these 70's obscurities are super rare, and lucky for me, worth big $$$.
Here are just a few in my collection:
De De Lind - this one is worth about $2000.00
This has got some great contrasts between intensity and quite moments. Also some great flute playing.

Alphataurus - this is worth about $1200.00
This has got a great triple gate fold sleeve.

Museo Rosenbach - this is worth about $2200.00
This one also happens to be a masterpiece of the genre. As good as any of the big prog bands from England.

I have quite a few more at similar prices.
I also own a lot of rare French and Spanish prog, but even though they are comparably rare, they never reached the prices of the Italian rarities.