We don't pay this much we pay aroubd £2000 a term. But I realise that this is not a small amount of money and that many peopl cannot afford to do this. And FWIW I have been in the situation where I couldn't afford this in the past.
I'm a teacher, and so not very well paid. Dh is am RAF officer, so well paid but out joint income does not reach the £100,000 mark (or even close). However I realise that we are very fortunate and earn considerably more that the national average.
We don't have the money 'spare' as such. We could easily find homes for it, we could have new carpets, replace old furnature, take expensive holidays (we have always tended to go camping, not this year dh is too ill). We wear old clothes, never buy 'designer', seldom go out, but this is our choice. We drive Ford cars, nothing flashy.
That said, we are not going 'short' to send them. I have been in the position of having no money in the past, and recognise the difference.
Even sending the children to private school we live a comfortable life. If we didn't pay for school we could afford other luxuries.
We do work hard. But so do a great many people , who are not lucky enough to be paid as well as we are.