Its really quite simple as to why prices have gone up hugely.
1) devaluation of the pound - which immediately adds to cost of imports. In 2016 we got about €1.20 for every £1. Nowadays they are pretty much €1 = £1. Ditto for US $
2) cost of doing business - fuel, labour and money costs have all gone up hugely. Partly due to devaluation of £, partly due to lack of supply and partly due to rise in base rates so cost of money has gone up.
3) Blue Tape - in the past about 40 to 50% of our imports and exports were within a common customs union, so in practice no customs procedures were required at all. You ordered something from a supplier, they popped it in the post and it arrived a couple of days later. You paid for it on order, and your customer paid for it day after it arrived.
Now everything that moves in and out of the UK is subject to customs declarations. Everything has to be recorded, everything needs a customs code so that we can generate a huge amount of data that will tell us precisely what???
A friend runs a wine importing business. There are something 500 different codes just for wine from France. Get the wrong code - products don’t get through.
Exporting product, again get the wrong code, or make a minor mistake, products do not get through.
VAT - again in the past this was paid at point of sale, you then declared imports and exports on your VAT return and whole lot netted off at a government level. Now has it been paid, reclaimed etc etc etc.
And our customs system really hasn’t had all the resources to make it run efficiently, nor for that matter do all the suppliers outwith the UK.
And given the huge extra workload, it affects all imports and exports.
So individual businesses now have the costs of managing all the Blue Tape, costs of chasing customs, or their distribution partners (DHL, Parcelfarce, Hermes etc) to try and find out where the goods are. And then have all the costs of managing their clients expectations.
So going back to the OP question, the gunshop is having to field repeated questions of “where is my …..”. And six minutes of time on £10 an hour min wage costs £1.
And all of the above now means a large chunk of our goods are now taking two, three or six weeks to get through. The big boys are fine - they have the resources to fast track stuff. Little companies do not.
So now you go to your supplier, pay for the goods, and your goods turn up a few weeks later and then you can sell to your customer. Chances are you are using some form of credit to fund these orders and these days that’s costing 5% per month. And this cost is additional to all the above costs of getting goods into and out of the country.
So your prices go up. And this adds to inflation. And all the embuggerance means that UK as source of supply becomes less favourable. So £ is devalued, and cost of government borrowing increases because the markets have less faith in the UK.
This cost of government borrowing is a rise in interest rates, which the Bank of England and the Government will explain away as the medicine required to stop inflation.
And this is a never ending downward spiral that is a direct result of withdrawing from international markets. And a failure to develop new and increased trading relationships.
And whilst those in power stick their heads in the sand business will suffer and our prices will increase.
Don’t worry though, in places like Zimbabwe you pay well over US $100,000 for a very basic pickup truck so we do have a way to go.