This article I thought was quite good:
Brexit: Early financial settlement won't be 'forced on UK' - BBC News
A chunk of it is for the 'cohesion fund', the bit where we have to pay for shiny new infrastructure in Eastern European countries whilst we can't even get a new runway at Heathrow, or HS2, and our motorway 'improvements' involve removing the hard shoulder. But this is only up until 31st December 2020, so not long after Brexit is sorted anyway.
Then there is our share of the pensions black hole in the EU to date (again, fair) and our share of the EU's accounting deficit (probably fair, if they can produce suitable accounts).
What it wont be is a €60bn bill on the day we leave, but payments spread out probably in line with what our regular contributions would have been, on a sliding scale.
But it does give us a strong hand when it comes to retaining single market access. "Yep, we'll pay our fair share, if we get our fair share of the assets back, and we continue to get unrestricted access to the single market".
I fear a good deal is on the way. All this talk of bad deals and no deal is a bloody good way for May to announce a great deal in 2019, about a year before a General Election... Of course it wont be 'as good' as EU membership, but to the ordinary man and for business the sky wont fall in and we aren't falling off a cliff.