That applies to a lot of stuff, Comet have lower prices for some stuff ordered online. I think they're trying to discourage people from using their stores.
....and a growing trend that is too.
Used to occasionally pop into Banbury Trailers for odds and sods while at the same time they operated a website to sell their wares and then they suddenly announced on the entrance door at Banbury you can only buy from them off the Internet even if you were local!!! Collection on the other hand not a problem. I still think it's daft though!!!