Something I think about from time to time

[Samus-Fan]

I'm gonna agree with you on parts, and disagree on others.

Some bands I know of such as The Killers changed to a more mainstream kinda music, but I don't think it was because they wanted more money by fulfilling what the popular music is.
I feel their new style is more of their type. Like they're more comfortable with it.

However, some bands like you said that sound exactly the same can be a good thing. It keeps the same kind of fans, not losing any and not gaining any. It's like a very defined PH.d.
Other bands like Muse sound completely different every time. And although I like that, it isn't a good approach in my opinion, and not saying it isn't up to the band, they can do whatever they want and true fans will listen to it.
But it is like a restaurant changing a recipe of a food you used to love every time you go. You don't want the change, you want it to stay about that same.
There is a way for the same type of music to sound different, while keeping the fans you had together, and gain more. Successful bands can do this, and do. Metallica is a great example.