Yes, that's how I and various consumer monitoring groups are looking at it. It's a concern.
Brand prices jump around, they always have. Certain things sell cheaper at certain times of year. Bailey's for eg always gets cheaper in the six weeks before Xmas because they make most of their sales during that time. In addition certain things are at their cheapest in one shop for a time, then another for a time and so on. It tends to balance out - eg you'll get your cheap Bailey's but your Surf powder (for eg) will be more expensive, then a few months later in the same shop Surf will be cheaper than anywhere else, while say Lindt (in the run-up to Valentine's) will be more expensive than anywhere else. So you're not saving money by sticking to the one shop, over time but also you're not losing money either - you save a bit, you lose a bit, it's all ok.
Add in even basic loyalty cards and it becomes much more targeted. Because they know that you buy Bailey's but they also know you buy Surf. They know you buy Surf regardless up to a certain price point. So at the point baileys goes down in price Surf increases to the very limit of your pinch point and stays there throughout. Same across your shop - they'll increase as they reduce knowing which items are specifically co-occuring with the greatest frequency. They'll do it in tandem with other big retailers who will have similar ebb and flow. One of them will be the cheapest for a number of key goods at any one time, one of them will be the most expensive, and your data lets them know which to choose.
Again, you're probably fine with that, it's a bit manipulative but hey you'll get your pizza express voucher in return so it's all good.
Now add card pricing into the mix. Eg this Lindt 'deal' - other items will increase in price to compensate for it, other retailers will sell it at a higher point, then they'll all swap around in six months and (eg) it'll be cheaper in Sainsbury's after that, with something else more expensive in Sainsbury's to compensate for it. And that's just the swings and roundabouts of supermarket shopping. But now, unless you're signed up to the loyalty scheme, you'll never get those swing prices. And as more and more shops require you to give your data in order to get the swing prices, you will be buying everything at the other end of the scale, without ever getting the dips to compensate for it. You will be perpetually overcharged, forever.