When Betanysports send you an offer I believe it is 6X RO. Betonline is the most strict and believe their 50% FP are at 10x RO, Bookmaker/Justbet is a cash bonus and is 6x if 15% or 8x at 25% and 10X with their 100% FP. Bovada beats them all with a weekly 5X Ro 50% cash every damn week and some weeks goes up to 125% cash 5X RO.
I don't know where you all are seeing 20X RO but it isn't from the BMR linked books I mentioned.