Re: "Has whoever sold the domain actually got the money?"
"Cash" when used in the business world in the US means currency. Doesn't have to be paper currency, it could be a bank transfer or cashier's check. They basically mean anything that immediately changes your bank balance, as opposed to paying in other instruments that may have strings attached or not be easily fungible like stock, bonds, real estate, etc.
When dealing with real estate, sometimes you'll have buyers making an "all cash offer". That means they won't be taking out a mortgage and have enough to fund the entire purchase price themselves, not that they will show up at the closing with a suitcase stuffed with $100 bills.