Indeed they are. Anything on Saturn goes for big bucks, especially ones with handmade covers. Impulse did a solid run of re-releases in the mid 70s that are much more accessible.
Top 10s are always tough, but I'll give it a shot. I have a penchant for the obscure, but if I were to consider total output, my list would be (I know I'm leaving some out)...
- Arthur Verocai (anything he arranged)
- Joyce Moreno
- Jorge Ben
- Milton Nascimento
- Edu Lobo
- Nara Leao
- Elis Regina
- Marcos Valle
- Gal Costa
- Joao Donato
And a bonus top 5 groups
- Tamba Trio
- Novos Baianos
- Azymuth
- Quarteto Em Cy
- Dom Salvador's groups (Rio 65, Salvador Trio, etc.)
For a deep dive into the obscure stuff, I used to do a podcast from my collection. Lots here to keep anyone busy.
My favorites are a bit later – Lanquidity (1978) and Sleeping Beauty (1979).
A good start might be the lone release on Savoy, The Futuristic Sounds of Sun Ra (1962) – China Gates is such a hypnotic jam.