Easily. It's really down to market-share and revenue protection. Whilst there's a large draw for traffic from the UK to the states during this time of year, the draw is very limited ex USA. Additionally, although it's not stated, the airlines monitor one another quite closely and tend to pretty much match fares.
We also need to keep in mind the additional taxes we are now faced with as well.
Finally, the US has 11 different 'board points' for traffic to the UK. We have Five...sometimes six. Because the US has lost so much money for travel within the states, the prevailing carriers have now decided they will saturate the Atlantic in the hopes of building not revenue but cash-flow. It's rather frightening, but UK and many EU carriers are now prepared for the fight.
If you'd like to look at historical fares, the best group to use is Kayak.
http://www.kayak.co.uk
Be well
Fr Bill