There are reasons to think the headline figure could be lower, for example deciding to stop trading with the EU.

But also reason to think higher, for example additional cost of engaging customs brokers, freight forwarders; training/hiring staff; purchasing software etc. https://twitter.com/globalvision_uk/status/1283022825939521536

I really don’t understand what people think there is to be gained from pretending putting up a customs and regulatory border with the EU won’t be costly for business. Of course it will.

Erecting a border is going to create a lots of jobs in the UK and see the customs advisory/intermediary industry grow significantly over the next few years. But this is all money that was previously spent on other things.