They face the stark choice of making concessions to keep us in and preserving the EU's existence, or trying to make up the shortfall in funding when we leave and watching the entire EU disintegrate when there isn't enough money to go around.
We currently pay in more (gross) than seventeen other member states combined;
If you look at NET contribution, we pay in more than anyone bar Germany.
If we leave there are only about six or eight other net contributors at all... they cannot make up the shortfall.
The EU will protect itself by agreeing to a modest reduction in our contribution and also to us being exempt from free movement. The alternative is we invoke article 50 and the EU ceases to exist.
This is wrong. Very, very, very wrong. The UK's net contribution of +£8.5 billion pa to the EU simply isn't that much money. Germany would make that up on their own if they had to in interests of saving the EU. Even if they couldn't, Euro interest rates are negative. We'd simply borrow the money (and get paid to do so) in order to cover the shortfall. 8.5 billion pounds is statistical noise compared to the economic fallout of letting the EU disintegrate. It's not even close to a sum that would force Brussels into concession. Much more worrying is the impending loss of trade due to new tariffs and lack of investment due to an uncertain business climate. But I feel the EU has no choice but to weather the storm. A good deal of foreign investment and jobs being shifted from the UK to Europe should help soften that blow somewhat.
From a continental perspective, there was already a degree of resentment towards the UK as it was felt they had the sweetest deal of the 28 - controlling their own currency while still enjoying the benefits of full membership of the EU. Not even touching on other minor things like Britain not taking any refugees etc. It is very unlikely there will be any political will for making concessions to the UK in negotiations. I can't predict what will happen, but the UK won't get off lightly.
I also think that from reading only English language media sources there is a misconception of the sentiment toward the EU on the continent. Of course there are the fringe populist politicians making headlines with outlandish statements in every country, but there isn't any serious desire to abandon the EU project.
This will hurt the European economy, (it will hurt everyone) but it will hurt the UK economy far more. It's a very bizarre decision. It's like treating a sprained finger by amputating your arm above the elbow.