Isn't it the other way around? If the flagship had a higher budget, it would've been better able to afford a pricier actor.
Except that NBC's rationale for killing Law & Order was that it had become too expensive (to the point that it was trying to get TNT to fork out anywhere between a quarter and almost half -- depending on which source you believe -- of the production costs for Season 21) in light of plummeting ratings, and the budget had already been slashed in recent years (which resulted in Sam Waterston taking a significant pay cut and a lesser role in order to stay on the show). Given that Erbe's contract, after so many years, had to have been providing her rather significant compensation, I really don't think she would have been re-hired for Vanilla.
Was she axed, or did she choose to leave when D'onfrio left? I haven't found anything saying either way.
D'Onofrio had been looking to leave the show for quite some time (which is why the "split detectives" concept was introduced, in order to induce him to stick around a while longer). Erbe had always been non-committal regarding her future. In interviews, at least, she had never conveyed any sentiment similar to the "we're a package deal" statements frequently espoused by Mariska Hargitay and Christopher Meloni over on SVU. No official statements have been given regarding her departure (it's rather telling that of the departed cast, only D'Onofrio has said "Yeah, I wanted to leave," while the others have remained silent), but if you read between the lines, given the dropping of the "split" detectives and the focus on Nichols, the hiring of a cheap (and terrible) actress in Saffron Burrows () and an equally cheap B-lister in Mary Elizabeth Mastrantonio, coupled by the reports that Criminal Intent suffered yet another budget cut after last season, it's not too difficult to get the picture that the ax fell and costs were minimized. I could be wrong, of course. The happiest answer is that Erbe decided her time was up and she wanted to bail. But when a show with such a poor financial history as Criminal Intent overhauls its entire cast, like seaQuest many moons ago (for example) ... well, you know what they say about smoke and fire.
Strange & improbable. Still, I'd be happy to hear it, since Trial by Jury was always my favorite of the spin-offs. (Although, you can't beat Conviction for eye-candy.)