I don't think it was 'vulgar' but it did cost a vast sum - but that vast sum is presumably in proportion to their parents' incomes!
And if the Middletons are rich I am not going to feel or begrudge them because they are an ordinary couple; it's just that she had a good idea and started a business at her kitchen table which has proved to be a very lucrative money-spinner. They still live in the UK, presumably pay all their taxes, give employment to others.
I wish I'd had a good idea like that too!
To think that London, or anywhere else for that matter, does not belong to any one demographic