I used to be able to deliver same day to NL, took some organising but possible. In low volume times, I've seen the cost to deliver by 40ft artic as low as £400.
A lot of dairy products come in from the EU. Without a deal, each one will need to have official milk certificates stamped by a vet. The cost of the Vet used to be around £600 for half a day, I would squeeze as many as I could in that window, but getting it all to happen was a nightmare. Documents by snail mail from Defra (no damages or you need to redo, twice for vet, demurrage for hauliers, handling fees for warehouse, no sale), trying to ensure the truck and Vet were there at the same time, etc. Guessing they also need an EUR1 form to get into the EU now, that has to come from the chamber of commerce, not much different than defra but you can at least fill your own form online, before its sent via snail mail.
When we start talking boats, apply the above but factor 2 times delivery, cost of container hire, cost of handling fees at port. And there is a reason that stuff was left in Lebanon, the port storage fees are stupid high, noise levels times 1000 if something ends up in storage at port.
Then there is the inco terms, they can be found online. I would guess most of the EU operate on FCA. They are all about the point of ownership. On certain terms, a third party is required to hold the cash whilst the goods are delivered.
Factor in demand changes, currently in the EU, if its selling better in another country, we can just move it there as long as the language on pack is good. That won't be the case outside of the EU, returns and stock moving just won't be possible as most largely depends on the country or origin. My experience is when new trade lines open, the demand is always over the top and quickly gets reduced. With slow reaction times and long lead times, quite often you will have produced for the next one before the demand drops.
That cost WILL be passed to the goods as part of the supply chain costs. A deal is a must or food banks will be in the rise.