But the supermarket pricing has been like this for 30+ years, the only change is the offers are restricted to loyalty card holders. There are products I've bought for a long time where they go down in price every few months on special offer. Things like Ginsters pasty, New Covent Garden soup, Muller yoghurts, Colgate toothpaste and other branded items have done this for 30 years. For example the New Covent Garden soup is currently on offer at £1.50 down from £2.45 at Ocado, in a few weeks it will be back to £2.45 at Ocado but on offer at £1.50 at Tesco instead. Seven years ago it would be £1.80 and then down to £1 on offer, both the full price and regular price have increased as have many other food items in the last seven years due to the wars and other factors.
Yes Tesco and Sainsbury's lock their promotions to card holders, but Ocado and Asda will often have the same discounts without the loyalty only thing. The promotions have always been like that and still are at most places.
Do you have any links to items that are 2/3 off when on promotion? I've not seen anything that significantly below 50% off for a long time.