You’ve still not adequately explained why his business is going to fold under Brexit.
In fact, you have to concoct a fairly robust fantasy for this to be the case.
Presumably, his business is going to suffer because his input prices are going to rise. For that to happen, the following things need to happen.
First, the UK will be applying an import tariff to goods from the EU. Perfectly feasible, especially under WTO rules. However, we previously imported certain goods with no import tariff whatsoever. To do that, we had bilateral deals. The only reason we won’t get a bilateral deal is because the EU won’t want us to have one.
Let’s assume, for the sake of argument, that a tariff is imposed. For your mate to achieve perfect business oblivion, he will not pass his costs down to his customers, even though that is what every other business does, even though people that are prepared to spend £4.5K on a bike will probably be prepared to spend say, £4.8K on a bike. Your mate will have to retain his present prices, regardless of the rise in input costs, for the benefit of his affluent customers.
I guess the 35K question is does that sound remotely likely?