A third party earns transaction cost created by time, it can earn more if it tries some more risky moves.

When trading on the Internet, because of trust issues, we rely on a third party. Besides the internet trading, we need a third party for many other purposes, such as when we sign a renting contract. In these cases, we give our money to the third party and only when we receive our goods or services that the seller guarantees, the third party will then transfer the money to the seller.  When the money is held by the third party, it is the third party's asset. If the third party does not want any risk, it can receive a profit of the money it holds times the interest rate at the time. However, if the third party is aggressive, it can use the money for investment which will give it a higher return but more risks. Now the third party is like a bank, buyers save their money in the third party, but the sellers will take out the money at a particular time. It is good that the third party does not need to pay interests, but it has to manage its fund more carefully because there are no long term savings.