Sainsbury's do it too. 50p for 250g (or ml, I can never remember which way they measure it!) I only ever buy this one if I need it. I can't eat it on it's own and only use it in a recipe.
The one in Tesco is a 500 tub
It must be a local shortage as Tesco don't have it and we don't have a Sainsburys
Our manx supermarket told me it had been discontinued , can't get hold of quark either.