Try pricing up flights to the States and you will find that last years 300 quid flight is now 550-600, and indeed the Charter carriers{TCX TOM etc} are even more pricey................680 quid to Orlando and then the cost of bags and seats next to each other and food.
Airlines alter fares all the time to match demand. If demand fall, fares will also. Maybe flights are already filling up?
Im paying 245 quid for 2 to DLM on Easyjet, but on the same day in May JET2want 570............
I have always found LS to be quite pricey but they always seem to have full planes! You should see some of the winter fares they charge to the Canaries!