I think Home Improvement suffered from this. In the last year, money for the other cast memebers became too much of an issue and hassle for Tim Allen so he said the hell with it. So that’s sort of what you’re asking about.
IIRC, the WB cancelled its highest rated series, 7th Heaven, because the costs were getting too high.
Of course, then the WB merged with UPN as the CW and worked out a deal to get the series back more cheaply, so it was renewed for another year, so it might not quite count.
Well, I’m not really sure how popular it really was, but Charmed really had to cut costs in the last couple of seasons. Phobe lost her flying power because it cost too much to string Alysso Milano up and haul her around the set.
Aparently both she and Holly Marie Combs who were both Executive Producers, didn’t get take any salaries just to keep the show on the air becuase it was so much fun to make.
Cheers never lost popularity, but by the final season even supporting actors like Ratzenberger/Wendt/Perlman were earning millions per year while Danson and Harrellson and Alley had record-breaking contracts and the show was making less money than most far less popular but moderately successful/long since forgotten sitcoms.
Mad About You- by the end Helen Hunt, who’d won an Oscar, was earning $1 million+ per episode and Paul Reiser, by the terms of his contract, could not be paid less than Helen Hunt, and the $60 million earned by the two stars each year ate the profits.
Sanford & Son was still hugely successful when it was cancelled, but its two stars had contracts up for renewal and both wanted to move on, so they asked for absurd amounts of money by the standards of the time. (Today, even adjusted for inflation, it probably wouldn’t be in the running with a Friends or Mad About You salary, and of course today they’d never cancel a show because of lunatic compensation until the second or third season of lunatic compensation packages.)