To spend money lavishly or freely, usually on something that is nice to have but not something we really need.
"Joe just splashed out $500 on a new watch."
When we keep money for a large expense in the future, we save up.
"I'm saving up to buy a new car. I should have enough by next year."
We pay off something when we complete payment on a debt.
"I'm going to be paying off my credit card bill for months. I used it a lot when I was on holiday."
We cough up on things that we don't want to spend money on. When you reluctantly spend some money you cough up on something.
"I had to cough up £70 just to have the dripping tap fixed in my kitchen."
When someone tries to cheat you out of money, they are ripping you off. You are ripped off when you pay too much for something.
"I don't think this necklace is really worth $200. I think the salesman is trying to rip us off."