Laugh all the way to the bank
Definition 1 of 1
Pro Tip 1/3Situational Use
Use when somebody gains a significant benefit, often unexpectedly or easily. 
She bought the painting for $50, and when it was appraised at $10,000, she was laughing all the way to the bank.
Pro Tip 2/3Possible Negative
It can imply the money was earned in a way that might be seen as immoral or unfair by others. 
Though his tactics were questionable, he was laughing all the way to the bank after the deal.
Pro Tip 3/3Figurative Expression
Understand it's a figure of speech; one doesn't literally laugh to a bank. 
They won the contract over the bigger companies, laughing all the way to the bank.