Concerning Steinbeck's The Grapes of Wrath, the quote you cite is during a conversation about low wages. Tom Joad says:
"Well, s'pose them people [the thousands of people needing work that pays a decent wage] got together an' says, 'Let 'em rot.' Wouldn't be long 'fore the price [wage, rate of pay] went up, by God!"
What Tom is unknowingly talking about is trade unions, of course. He suggests that the workers strike, until the owners of the crops pay a decent wage. Once the crops are ripe, they rot quickly if they are not harvested. Tom suggests that the owners will be willing to pay a better wage, rather than let their crops rot.
The young man Tom is talking to informs Joad, though, that that has already been tried. And the owners stopped it from working by throwing the leaders in jail.