Well, pay for what? if it is money received from the EU since the referendum then yes they should bring it back. Other than that I don't see what they should pay for exactly
Previously mentioned budgetary positions and projects over the next few years, to which the UK has committed itself. Plus a lot of pension payments etc.
Anyway, the cost doesn't necessarily have to be 60 Bio. €, they could also be lower (that's just a starting point based on the UK's current liabilities within the EU).
Part of a comprehensive deal could also be a lower Brexit fee, but better trade conditions etc.
Or the EU cuts down their future budget, to avoid a shortfall causes by the UK not paying any longer, which would also be a nice option.