[relix]

Robinhood users are unsophisticated (= to put it another way: "idiots" who don't have advanced data to inform their trades). This means taking the other side of their transactions is more likely to be profitable than taking the other side of orders coming from, for example, RenTech. Knowing that an order comes from RH (or in other words, not from sophisticated traders) means it's more likely to be profitable for the market maker to fill it. This difference in EV is worth more than $109 to the customers.

It's essentially a "first dibs" approach to fulfilling a transaction. By law it's required to fill at the best price available, so there's no difference in price, and it may even fill quicker if it's in between the bid/asks because of the reason explained above.