Expedia doesn't get the commission, but the hotel is forced to offer a rate that matches its "most-favored nation" agreement with Expedia etc. so its prices will reflect the [base + commission] rate wherever you find them advertised. This results in a 15–30% hike over what could otherwise be the lowest rate, akin to similar recent complaints abouts Amazon's aggressive price-matching impositions on third-party sellers.

It's a bit unclear; the point the article makes explicit is that the commission raises prices when coupled with the most-favored nation agreements. There is the mention of "supplier-funded promotions" as "kickbacks", which might be from direct bookings.