CBS contestants had always been allowed to keep up to a certain amount of loot. From '78 to '93, contestants retired after winning a certain amount, but could keep up to a higher amount. For instance, contestants from '78-'81 retired after winning $25,000 but could keep up to $35,000. All limits were ditched in '07 after two TPIR players won over $140k.

As for ABC, according to a Google Groups blog which quoted an excerpt from an article from the July 1975 issue of Newsweek, ABC contestants could keep up to $30,000. Apparently this was changed by the time
You Don't Say! premiered that same month because on that show, and Break the Bank, which aired the following year, Tom Kennedy mentioned that players continued until winning $20k but kept up to $25k. This limit soon changed so that players/teams continued until surpassing $25,000 and they kept every penny! The retirement threshold had been lifted by '84.

Stumpers is believed to be the only NBC game show where contestants retired after exceeding a certain amount.

Any corrections are welcome at [email protected].
'72: $25,000
'78: $25,000-$35,000
'81: $25,000-$50,000
'84: $50,000-$75,000
'86: $75,000-$100,000
'90: $100,000-$125,000
'93-'07: $125,000
Stumpers ('76): $20,000+
'70: $30,000
'75: $20,000-$25,000
'76-'84: $25,000+
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