> In 1971, Terry Ellis, the co-founder of Chrysalis Records, paid him a flat $1,500 fee for the three paintings which would comprise the album’s artwork
It is too bad he didn't negotiate a royalty agreement, but then they might not have given him the work, either.
FWIW if he had invested $1000 in the S&P 500 on January 1 of 1972, that investment would be worth about $100K today, according to some online calculators that I tried.
Granted, investing is a lot easier, now that online brokerages exist. It was probably not something that many artists did back in the '70s.