Fares are indeed much higher since the last sale was offered.
However, capacity has been reduced, there is no Silverjet/MaxJet on the route to drive down prices, Gordon Brown has doubled APD and fuel prices are rising. On top of this the Government is driving the economy into a hole, both causing and necessitating a fall in the value of the pound.
It’s off you cannot see cheaper fares, as there are plenty of tickets for long weekends to NYC at £1486 rtn. I don’t think that’s great value personally, but it’s certainly quite hard to get the £2800 price you quoted (perhaps you are planning a Valentine’s weekend jaunt, which always inflates prices, sale or not).