I was happy to see, on Amazon's site, they have some affordable Super Sentai and other Tokusatsu music available for purchase. Its mostly older music collections -- and their "buy it new" price isn't usually very fair -- , but the prices for used CDs are sometimes very affordable! I was able to buy music of Juken Sentai Gekiranger (both the complete series, and the character songs CD), and the collection of Magiranger Music. (You can find that here.)
You sometimes have to use sites like CD Japan to check out (and sometimes hear) what music is on what disks. Sentai Music is cheaper to find, but Kamen Rider Music seems stubbornly out of reach on many occasions with higher prices.
The reason I wanted to get Magiranger music was mainly because of the EPIC song they have for MagiKing (when they combine into a giant robot). The song seemed perfectly matched with a great introduction of MagiKing on the show, which you can see the fight here.
And here, the song is performed by the musicians behind it
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