OhHiii said: "Dirty Rotten Scoundrel said: "but that means gambling on splashing around much more cash than they seem willing to part with."
The nuance you’re missing is that this was the amount of cash they were willing to splash around with Andrew in the role. And he likely had first refusal in his contract, so he had to be offered first. If there was someone with a bigger name in the mix, I am sure the purse strings would loosen.
Another part of the equation (I think it's been mentioned elsewhere in this thread) was that Tammy Faye was Andrew'Andrew's first stage gig in a while; the last one being The Boys in the Band where he had a supporting role. Beyond that he mostly did voice work or supporting parts in movies or TV - there might have been a sense he wasn't necessarily a draw as a co-lead (especially since, as has been mentioned, Tammy is the more substantive part) and his pay was calculated based on that. But the success of Gutenberg would have changed everything, proving, in New York at least, that he was a genuine draw. It sounds as if maybe the producers might have been trying to keep him at pre-Gutenberg rates and he didn't like that.