A lot of thoughts here.
One, Bill Ward's unreliability is not "supposed". He ended up forcing the band to cancel at least one tour, possibly two, and several shows in between. He couldn't cut it. I saw the "The End" tour, and while Tommy Clufetos wasn't my first choice, the show would have suffered if the drummer couldn't carry that every night at that level. It was NECESSARY for that show.
Two, I just saw Maiden not four months ago, and Nicko was amazing, but let's not kid anyone here: Nicko is 67, and Maiden isn't a "Charlie Watts" kind of gig. There's a shelf-life on Maiden. I don't know what it is, but there's a shelf life on Maiden. Some of the best drummers in rock have shown or are starting to show their age, and there's no crime in that (Collins, Peart, Alan White, Ian Paice has missed shows recently, Peter Criss, Bill Ward, Bill Bruford).
Three, there's always been a history with Kramer. He's had his own drug problems, and he's battled other issues as well. Tyler - originally the band's drummer - has frequently battled with Kramer (as you might guess, there's been a disagreement since 1975 as to who came up with the signature intro pattern to "Walk This Way", a song Kramer does not have a writing credit on). I do not believe this is the first time he's been told "clean up your act". Is it fair? Of course not. But I'm not sure who decided it was supposed to BE fair.
Four, the money thing... I don't know. I have read that the replacement - Kramer's drum tech, John Douglas - is being paid out of the money that would have gone to Kramer had he performed. I'm surprised at that, frankly, though I would guess that that is just a cash flow mechanism, a way of distributing funds. Aerosmith is almost assuredly a "corporation", and unless Kramer doesn't have a share in that corporation - entirely possible, though not the most likely option - I can't imagine this is about money on it's face.
They also have a residency going on here in Springfield, MA at the MGM Casino. My brother-in-law went to see them in... I think it was August, certainly it was this fall, and I'll ask him if Kramer was behind the drums. I know he did say they sounded really good.