I think you must be reading it wrong, becuase -
MPS4's 235/35/19 from Black Circles are £151.20 mail order price
MPS4's 235/35/19 from TyreLeader are £147.78
I'm running 235's all round on my Mr's 8p & have not noticed any differance in the handaling, but in terory the rear grip level will improve slightly due to a bit more rubber on the road.
HTH?
True but they do give you £40 off when you buy 4 on black circles
I think my auntie has a Costco card though so may go there