Falcom have quite the selection of albums available for download from Amazon's U.S. MP3 store, ranging mostly from $8 up to $16 for some of the double-disc albums.
Amazon's Falcom MP3 store
Included among the selection:
Ys Celceta OST
Ys Seven OST
Ys I & II Chronicles OST
Ys Origin OST & Super Arrange Version
Ys Oath in Felghana OST & Super Arrange Version
Ys VI: The Ark of Napishtim OST & Vocal Version
Ys Music of Ancient and Modern Times
Zwei 1 & 2 OSTs
Xanadu Next OST
The Legend of Heroes ~Kiseki series OSTs & Super Arrange Versions
the entire Zanmai series
...and various others. If you're one to download MP3 albums then it's worth a look!