I mentioned this in another thread (I was ranting about the RejuveNATION offer).
In the UK VAT is applied at 17.5%. MEB rates will have 20% off, but when you check the rate rules it always says "excludes tax". The savings are actually paltry and the 20% discount draws people in and mislead. In fact I wouldn't be surprised if Marriott could be caught under the Trades Description Act in the UK.
I think someone at Marriott thinks that all their guests are thick. I have stayed at hotels where there is a DB&B package and the rate works out at £25 a person more than just B&B (I did this when using AMEX BBs as it was only on DB&B). When I asked what the allowance would be for dinner I was told £20! I had to point this out at two separate hotels and they then made the dinner allowance £27. Either they think we have no idea or they have some number cruncher who really has no idea.