It is not about the cost - they are really not a bargain or cheaper. It is about the lifestyle, the holidays you want, and ability to 'just go'. I can brew up, I can take my food with me, move freely and to my own timetable, bike or canoe can go with me easily etc. Campsites are very social generally, or another way of putting it is there is no privacy...but for kids it is great to meet others and be a bit feral. They are warmer and more comfy than a tent, not as comfy as a self catering or hotel.
For me a campervan was the best purchase ever. But I am now able to go without kids at home on any weekend the forecast is even slightly good. I run mine daily so do not have another car.
Motorhomes, big and expensive ones for a family particularly, end up costing basically what a good hotel or self catering would - and there are comprimises. My camper is cheaper - it has less depreciation, cheaper to insure, maintain, park/camp fees etc etc.
The more nights I use it, the cheaper it is becoming. I do use it year round, most weekends, and in winter I don't always stay on a campsite. It cost £28k, plus fixed costs of around £1500a year (Tax, Service, Insurance, Breakdown) and fuel and campsite fees on top. But a year later it is still worth nearly what I paid and so far have managed 42 nights in it, plus any number of cuppas at the end of a mountain walk or cycle ride. So currently it works out at around £70 a night all in, and I have a few months of use yet this year so it should be a bit less than that.
But that is a van for only a couple - not a big camper for a family...And if the maths was for only a summer holiday plus maybe a couple of bank holiday weekends, it becomes extortionate.... Last week I was speaking to someone at a cafe who had admired my van - and said they bought a big van in lockdown, the kids didn't like it, they barely used it, and so sold it. Then worked out it had cost over £1200 a night....
So the moral is: wait for the kids to leave home, then use it more and more and more and more.