I've ended up with the idea that Michelin were allowing a lot more discount than in the past, and places like Costco that used to a very good place for Michelin and made even better if Michelin were running one of their money back or vouchers - but Costco now don't seem to keep an eye on how much others are charging for Michelins, so other than when buying winter tyres, I've ended up getting Michelins elsewhere.