These "up to" cash back or rake back numbers are a waste of time. Those mostly are max numbers that you would get after millions and millions of wager. Better to advertise the real numbers, those that you get when you start getting cash or rake back. Everything else is basically just false information casino love to throw out as bait so people join their site. The reality always looks different.
Well, it is not something exclusive from casinos and bookies to always use the best case scenario in order to sweeten their advertisements on the internet and get as many people on board as possible, it is something which can pretty much be found in any business which deals with discounts, promotions on products, and so on. There is always some small terms and conditions which people completely misses or decide not to play attention to.
But I agree with you, it would be great if they highlit some numbers which were closer to what an average gambler would get after claiming Cashback for the first time ever on those websites.