Schools fees are completely unaffordable for many people - it's completely out of the question. But for a few people, it is possible to find the money to pay if a fee paying education is wanted. In these cases, it can help to shop around. 'Top' public schools charge £34k per pupil per year for boarding. A minor independent day school might come in at less than £10k per pupil per year. Though to a large extent you might get what you pay for.
Next there are scholarships and bursaries which may or may not be means tested. They can reduce the fees by anything from nothing at all (you take the scholarship as an honour, but do not benefit financially) right down to all fees plus uniform and extras fully paid for by the school, though this is rare. Most scholarships are in the 10% - 50% bracket.
Next there are the family's priorities: what's more important - a large home, nice car collection, expensive holidays, independent education?
Some families have grandparents pay towards school fees. I don't think parents could ask for this. I think grandparents would have to offer.
There are also subsequent children to think about. Two or three children clearly double or treble the bill and sibling discounts are usually pretty derisory.
I know families who consider grammar schools as good as independents and a private school might be seen as a stepping stone towards entering a grammar. If a child passes the grammar school entrance exam they go. If their siblings do not pass, they remain at fee paying school.
Anyone toying with a few paying school needs to have a plan in place for where the money is coming from. Some schools have sharp fee increases as children enter each new school year. What was a really affordable nursery and reception place can soon become a nightmarish year 5 bill.
Lastly, you need to check which extras are included, exam fees etc. I have DCs at different independent sixth forms. At the well known school, we are charged a lot of extras, for example charity donations, alumni society, materials, breakages, weekend activities, hotel and meal costs for a national sports championship last weekend. My DC at the less well known place brought home a permission letter for me to sign yesterday. It was for an upcoming extra curricular trip away which includes a two night hotel stay and all costs are covered by the school.