Thats what the UK has spent to date preparing for Brexit. Not my figure – its the National Audit Office. See https://www.bbc.com/news/uk-politics-51762243
and we haven’t even started recruiting the extra 50,000 customs officials we need to handle all the extra paperwork “taking back control” involves. See https://www.ft.com/content/6cf7bba6-598f-11ea-abe5-8e03987b7b20. assume the total cost of each one is £30000 that’s then £1.5 billion a year!
still – we get blue passports (which we could have had anyway)