MM you've already admitted that they make a huge profit on their items and that's how they fund their "bonuses". The thing is alot of this profit will go to the directors, a small amount with go to the buyers and the rest keeps the business running. You've said they sell stuff around the RRP, this means that people are buying at or around the RRP, thus spending maybe 10-50% more on their shopping than usual (and what a mixed bag of shopping they get!). So people are essentially funding those bonus cheques by being talked into buying expensive items, many of which they don't really need (sound familiar?).
Have you actually added up how much you could've bought a typical LTW shop at another supermarket for? Include all the perks those supermarkets have too. Now realise how much out of pocket you're going to be. But wait! If you can get other people to be out of pocket (friends and family) then you start to be a bit less out of pocket with the chance to get a reasonable sized cheque (which after spending stupid amounts on stuff you could probably do with!).
That's where my morals kick in, knowing I'll make money because somewhere lots of others stand to lose it just doesn't sit well with me. Bit if that's how you choose to make your money well...