I can only compare with IAD, which tends to be in the same cost area. Since 2007 we've paid anything from £628 to £907: our recent trip was £845, and Sep is £791. All those took advantage of Sales, 6-9 months ahead, so I'm guessing [and
only guessing] that's where the fares are these days.
IAD currently running at £890

but I'm
hoping there might be a Sale in Jun/Jul to cover us for next Spring.