I would say that those losses that Drake had is a collaboration with Stake. I doubt that he has sort of a referral program with Stake, or stake give him money to gamble, or his bets are fake. He is using stake audience and stake as a brand to promote himself. Even if he has lost 500k, it is an investment in himself. Look on this as following: he has paid 500k, to promote himself on an
audience with 166 unique visits. Add to this social media, internet, talks and etc. And it cost him only 500k. Paid 500k, and got his advertisement running in the whole world for months
I think it aint much.
I am a bit lazy to do calculations and give super detailed info, but my signature campaign spends roughly 10k per week to advertise on the forum. That is 40k per month. And the area of audience is strongly limited with forum. But Drake advertise himself on the audience of the whole world for 500k per month (since this topic is month old).