The biggest supermarkets in Britain have gone bananas - you may think not for the first time.
Tesco has been advertising its "Price Promise" which claims to take (and here is the important phrase) "comparable grocery shopping".
This has been running in some form or another since early 2011. Sainsbury's complained to the Advertising Standards Authority (ASA) - claiming their reservations are not just sour grapes about an eye catching campaign.
Sainsbury's says Tesco was not comparing like with like. It claimed that there are some big differences in the products when it comes to things like ethics, place of origin and animal welfare. As an example - it says its own brand cheapest bananas are Fairtrade.
The ASA has ruled against Sainsbury's - supporting Tesco's argument that it was a fair comparison - despite some differences. It noted that Tesco did take some products out of the comparison if it believed the difference was a clear part of the shopper's buying decision.
Tesco says: "Price Promise is a simple proposition. It says that however you shop, whatever food products you shop for, we’ll compare your basket of shopping to our competitors’ prices and if your comparable grocery shopping would be cheaper elsewhere we will give you a voucher instantly."
There are some big issues here - if even the industry is battling over how much faith we have in these comparisons - what hope for the rest of us.
Second - the ASA says it would prefer not to be adjudicating battles between industry giants - it sees its main role as handling complaints from consumers.
But the biggest issue of all is this - to what extent (at a time of austerity) are shoppers concerned only with value - can they still also afford to care about values?