Just an estimate because commission contracts are strictly confidential - however the decision on how much to pay a travel agent, whether it's Expedia, or my own agency, is up to the discretion of the individual property, and in my own booking experience, these values vary widely by property or location so we can't really say that all independent hotels are paying the higher commissions. It just depends on how they want to market their product. Of course they have lower costs than a Marriott flagged property because they don't need to pay inflated franchise and technology fees to Marriott, hence some extra margin for direct marketing incentives, so they probably come out ahead on cost/margin vs a Marriott flagged property nearby with similar services and quality.