£1b/month would be 0.57 of UK’s 2018 gdp.
But knowing nothing about the £1bn number except that it came from a still-brexiteer I can’t give it much credibility.
UK GDP is $2.6 trillion, or about $200Bn per month, so a 1Bn a month is not a massive amount.
The amount is in and of itself irrelevant. What really matters is the ratio of that amount to the benefit the UK gets from free trade with the EU.
I only recently learned about the mistake-theory/conflict-theory dichotomy. I think the benefits don’t matter to a conflict theorists, only if insert-tribal-leader-here likes it. (There are at least four relevant tribes that support Brexit, at least five that don’t, and in one case they share a leader who has been carefully trying to keep both sides on his team).
I am almost entirely a mistake theorist on that axis.
Today, just half an hour ago, I saw someone tweeting that the EU was “bleeding the UK dry” by “taking” “£1 billion per month” [1] so I’m fairly sure that quite a lot of people did actually vote on the basis of the money.
[1] 1e9, or roughly 0.01% of the EU-(annual)-GDP per month