They set aside a big bundle of CRO at the beginning, for this kind of promotion. It helps them promote their platform and get new customers, because in order to get the 50% off, you have to sign up with them, and invest some money of your own (stake some CRO). It's not a straight-up, no-strings-attached giveaway. But it's no different than the letters I get in the mail from Chase Bank offering me $400 if I sign up for an account, and keep a balance there for 6 months, and transfer my paycheck auto deposit to the new account.