1984 Scrabble started with 10 time champions being able to win over $50,000 but then later on they capped it to a flat $20,000 after a 5th Sprint win and $40,000 after the 10th and final Sprint win.
Also when they went to the self-contained episodes, the Scrabble Sprint round went from $1,500 to $1,000, perhaps to balance the fact that a minimum of $5,000 was up for grabs at the end of every episode due to the Bonus Sprint.
Scrabble lasted about 6 years so I dare say when they went to the self contained format it didn't seem to adversely affect anything ratings wise. The only thing that did Scrabble in was the changing of the times with fewer and fewer traditional housewives being home to watch game shows, soaps, etc. as more and more entered the working world.