The economical part is important of course, but in an even wider perspective, its about whether you could accept a United States of Europe or not. To me, its a no,
This is always my favourite Brexiter argument, I think what I like about it is the blind ignorance which decides that all other European nations are all acting as one with the same interests, and it's plucky old Britain taking them on.
Let's take, for example, Poland. Poland as a nation has spent the last century and a half fighting for it's right to be an independent nation. It took on the Tsar, then the Kaiser, then got it's independence in 1919. Only to lose it again in 1939 to the Nazis, before being overrun by the Soviets in 1944 and remaining under their thumb until the early 1990s. Now why are you so certain that a nation which has known what it is like to be subsumed into a larger entity it has no desire to be a part of would acquiesce so wholly to a "United States of Europe" without a fight? Or is it because actually Poland has a better understanding of the EU and realises it isn't the sort of totalitarian monolith which appears to exist in the fevered imagination of many Brexiters?