Don’t all-season tyres have a slightly softer compound and larger tread gaps to give the extra grip? If so that probably means less miles per tyre, so the 50p price difference isn’t the whole story if they have to change them more often as a result.
Just doing my “look at all sides” and “devil’s advocate” thing…
"Man is born in freedom, but he soon becomes a slave, in cages of convention, from the cradle, to the grave."