People seem to be hung up on the EU membership fees. "Leave" say it's £350m per week, enough to build a new hospital every week, "Remain" come back with, we get half of it back in the form of rebates and grants, to which "Leave" retort, half isn't nearly enough and the EU uses the grants to fund vanity projects and effectively bribe prominent people, especially lefty arty people, to promote the EU cause.
However £350m per week (or £18bn a year) is not the big number in this debate. A few years ago the Institute for Fiscal studies (IFS) calculated that the total compliance cost imposed on us by EU legislation is £120bn per year, or more than £2bn per week! This is the amount the UK public sector and private sector combined must find to comply with EU law.
When you consider that 95% of British businesses have no trade with Europe at all, for most this is a completely unnecessary burden. This is the big financial win from Brexit, not saving the measly £350m.