If any band thinks they will make more money in what is usually a short career, they will take it. And regardless how early fans feel cheated after they go more mainstream, this wouldn't bother me at all.
If people want a band to give up financial security, because they had a copy of a copy of the first gig at The Dog and Duck, and are appalled at the treachery, then go start your own fucking band.
I always found that those who held these, sold out views, weren't musicians, singers, or performers. Never been in a band, couldn't play a fucking note, telling other people who could to forgo financial security because they are a bunch of pretentious pricks.
And no, I'm not bitter, our band never made it. But I can assure you if we did and some twat came up and said you sold out, he would have been knocked out. Pronto.
For us we were just too ahead of our time with our Jazz Funk Folk vibe.