If they price it cheaper then they will just cannibalize their own loads, which isn't particularly useful for them.

As for the ability to serve multiple airports in a metro area, that may make a bit of sense for carriers in Europe and even as far as TLV, but EWR is half again as far from London as TLV is, so the economics of it are rather different. CO would have to operate it as a redeye turn while TLV-LTN-TLV can operate same day. That's just one difference.

I don't really think that the market is there from the USA, particularly not right now.

Also, where on the Luton website did you see this? I just looked and see no reference at all to CO.