The EU has given us a lot of things that may not show up on the economic radar but make a difference to people. E.g. the EU is big enough to force airlines to pay compensation for late/cancelled flights. Good luck forcing that through as a country on your own.
Also remember the original reaaon for the EU, avoiding war. I worry that if it breaks up then a decade or 2 later someone will have a pop. That scares me more than many other things.