Can you give us your exact travel dates? I'd like to take a look. I'm curious about whether you've caught a particularly cheap pair of travel dates or that price is widely available.
I felt very lucky last month to grab a ticket from Washington DC to Madrid on April 8 and back from London on August 22 for just under $600. The same flights had been sitting at about $900 for at least two weeks. I was confident that the price wouldn't drop a great deal, but I figured it could (and eventually probably would) go up a lot, so I pulled the trigger. Since I bought my ticket, I've seen the price rise to over $1100, but today it's back down to $635. I'd happily buy at that price if I didn't already have a ticket.
Fares are volatile in general, but the amount of movement probably varies with the routing. NYC is such a competitive market that I wouldn't be surprised if fares there are a bit less wacko. However, I haven't been monitoring NYC fares and could easily be wrong.
Washington is usually a bit more expensive than NYC, and I think Madrid is usually a bit more expensive than Paris. If we were traveling on the same dates, I'd expect you to pay less than I have, but our travel dates are wildly different, and I have no idea how to factor in the impact of my April departure vs. your June departure.