Bogof?

To lighten the tone of this blog I'm back on dodgy supermarkets.
Son's on a health kick and is eating lots of tinned tuna (sorry Greenpeace), anyway the local Morrisons are charging £3.19 for 4 tins a rise of 20p on their previous price and the buy one get one free (bogof) offer has ended, so off we toddle to Tescos and they have the same product on a "bogof" deal, "great" I think then notice the price .... £4.99!!
So £2.50 a pack is a better price but how can they get away with saying it's buy one get one "free" when they're charging nearly twice as much?
Ended up in Iceland's and their price without special offers is £2.50.
So if Tescos price is correct and it really is buy one GET ONE FREE, they are charging 100% more than a competitor.
No wonder they make so much money as it's certainly not the only product they use this scam on, but Tescos is always packed and Iceland's is usually empty?

The words "rip off" come to mind for some reason.