I had to laugh at the Waitrose thing. Not being a UK resident for some reason I’d got it in my mind that it was some sort of family restaurant chain. Well, I was close!
Still playing Devil’s advocate, I would argue that by upgrading suitable Y pax instead of staff (at times when upgrades become necessary), the airline has the opportunity to promote their premium product and thus generate potential future sources of premium revenue. I don’t think that load factors in C (artificially pumped up with staff) will convince the punter travelling Y that he’s travelling in the wrong class. However, if he/she is lucky enough to get an upgrade to C and experience the product, he/she may opt to purchase a C class ticket on future trips. With perhaps few exceptions (and I’m one*) that won’t be the case with staff. If the promotion failed with Concorde it’s because that product is just simply way over-priced in the current economic climate. The same goes for Business Class. I think there is still a market for premium travelers but they now want value for money and many carriers fail in that respect.
* Yes, these days I actually pay for Business Class seats when travelling long haul because Mrs Avwoman and I are too old now to put up with the hassle of rebate travel - and potentially cramped conditions (if no upgrade) on long sectors. I do however, shop around for the cheapest (value-for-money) deals with reputable carriers.