These people will be paying around 600k tax assuming they are not leveraging efficient vehicles.
"Assuming" is doing a huge amount of heavy lifting, right there: pretty much everyone I know, as an example, who has their own business has their partner as a director (even if they spend all of their time shopping, golfing, or in the hairdressers), and their RRs and Porsches "through the company"............
SO, your back-of-a-fag-packet sums are likely way out, before you even start.
would people bother if it was just a few % different?
Bother with what? Your point is not at all clear.
But the fact is someone earning 300k has already paid 50 X more tax as well as a larger proportion of their income going to tax.
Just saying it is a "fact" doesn't make it so.
A basic rate payer has little-to-no opportunity to reduce their tax obligation.
Someone on £300k has a lot of avenues to do so; you acknowledge this yourself, in the same paragraph:
Its no wonder people find tax experts to reduce it.
Which is all perfectly legal.
And, all of your points are moot anyway, as the title of the thread was about
fair tax.
The people you're advocating for are the same people you have repeatedly said will sling their hook if they don't like it.
And yet, they're still here...........