I agree with pretty much everything you just said, but I don't think your conclusions are supported by your argument.
The problem is that you're implicitly assuming that Britain will be no worse off and then concluding that businesses will spot that so that we're no worse off.
Let's be realistic: the pound is worth 80% (give or take) what it was before the referendum. That isn't felt in your pocket immediately, but the effects works their way through the economy. Sure, purchasing power parity and the economy rebalancing will ameliorate that, but it's in no ways going to eliminate it.
Now, there's a problem with this analysis, which is that Brexit hasn't happened yet. This cuts both ways: the final state hasn't been reached, but also the economy's a lot more resilient inside the EU than outside, because the lack of tariff and non-tariff barriers helps with the rebalancing you describe.
So, for the future, a good question is: how are our preparations going? Well, the NAO says that they're barely going at all, the repeal bill says we're basically going to have to put up with direct monarchial rule to survive and to date we seem to be capitulating on every point of contention. What's worse is the points we're not capitulating on, because we're an 1/8th of the way through the process and haven't even got the status of EU citizens sorted out.
Even if the negotiations go well, we're talking about ripping up 40 years of settled U.K. law and replacing it with... well, ministers haven't decided yet, but they don't want parliament to have a vote when they do.
So, as I see it there's basically two possible outcomes here: 1) the EU retains most of the benefits of U.K. membership 2) hard Brexit. Die-hard Leavers have long argued that the EU is too complex, and the EU shows no inclination to make it more complex to suit Britain. Either way, we will be worse placed to trade with the rest of the world.
You're right, even in the case of hard Brexit the economy would eventually grow again. Would it grow as fast as it would within the EU? There's no reason to believe so. So we're looking at a huge one off hit and permanent reduced growth.
Sorry, this is quite long and probably not as clear as I'd hoped. I've also probably missed a fair number of important points. I haven't even touched on the _non_economic problems with leaving the EU. But I think it's clear that, while there are always ways to make money, Brexit is likely to be a negative sum game.