My recollection is that the prizes, once you adjust for the number of tickets required to get them and the difficulty and time involved in getting enough tickets, are severely marked up. There are undoubtedly more efficient ways to launder money. Not to mention that to do this with any significant sum you'd need a lot of people to be playing these games for a long time. Adults would raise a lot of suspicion, and kids would want to keep the prizes. The main value the restaurants like these offer is entertainment.