It's more than the risk free return. It's also fees. Whatever the fee percentage is, all in, to get a dollar out of the platform and back into cash on a winning

It's more than the risk free return. It's also fees. Whatever the fee percentage is, all in, to get a dollar out of the platform and back into cash on a winning bet, plus the risk free rate over the time period, that's your upper bound. Given the comments above about fees it doesn't surprise me at all to see 5-10% mispricing.