This is true, Full House was canceled by ABC not because of ratings, but because it was too expensive with the cast salaries and all the other production. That’s really one of the best examples too.
I was literally about to mention Full House being too expensive to keep around before I saw your post. That's crazy how we were on the same page.
Not to go off topic, but back then, a lot of sitcoms had longer runs than they should have because of goodwill. The network was happy to keep the show around, even if the ratings weren't that high. NBC would give shows additional seasons if they wanted. I found out from Todd Bridges' VladTV interview that Diff'rent Strokes was going to go another four or five seasons because it saved NBC when it came out. But Gary Coleman's parents kept harassing the NBC president for more money and calling him all the time, so they cancelled it. Plus, NBC had other shows out that were hits (Cosby Show, Family Ties, Cheers), so they didn't need Diff'rent Strokes anymore.
ABC picked it up for another season, but they cancelled it because Gary's parents were doing the same thing and demanding money again. Had they just calmed down and let things play out, Diff'rent Strokes would have been on for eleven or twelve seasons and they could have stolen more money from Gary.