By Jeffrey Strain. Treasury Bonds. Thus, a return is treated as a new transaction. We’ll use two different exchanges as examples, starting with Coinbase. How to Buy Bitcoins with Cash Those in search of a secure way to purchase bitcoins will be glad to know you can get them with nothing but cold hard cash. Visit our Learning Center. These exchanges differ in the fees you pay them for the transaction, the countries they are available in, and the limit of how much you can buy in a single transaction.