£150 million a week x 52 weeks = £7.8 billion a year (real cost to UK of EU-ish). So viewed in that way it's only about 5 years of EU membership costs. And if we borrow the money to pay for it now, the massive f*ck up our economy will become will mean rampant inflation will significantly reduce the real debt we pay. Of course there will be all the suicides, dead babies, unemployed, no money for the margins of society, less funding for healthcare, less funding for education et al. Society may fall - BUT ON PURE 2017 POUND NOTE TERMS it's not that bad. (Just ignore the dead babies)
Of course we'll have to spend a lot more than £150m a week to replace the things that the EU does for us and everyone else in the EU reasonably efficiently. Such as centralised legislation on safety, pharmaceuticals, environment et al. Even if we pass a law saying horses and hounds can hunt the greater crested newt, badger and slow moving pensioners now, we will need all those extra civil servants to pass those laws. And probably a few extra policemen to cart off the newt hunt saboteurs.