It's really simple in my mind. People either earn more (or in rare cases given more), have less expenses or spend differently. It's the same for how people afford anything. Some people don't have mortgages, some people have grandparents who treat them to an annual holiday, some people don't save and whatever is left goes on luxuries.
I have a friend who is wealthy though they'd never admit it and complain about the cost of living. Two high incomes, 5 bed detached house, 2 luxury cars plus a run around, huge garden, bouncy castles and swing sets, rental properties, free childcare by grandparents who foot the bill for things like parties, Christmas, meals out weekly etc. Their dc are 7 and 5 and have never been on holiday as they see it as a waste of money. Parents have holidayed once - their honeymoon. Another friend two high incomes, live in a detached £800k home (not London so at the upper end in their community), their dc do 4 sports each at private clubs, they spend more than 1.2k a month on sports not including all the petrol for competitions, they have an au pair, yet their dc have only ever been to a rustic cottage on a lake, they return to each year for 5 nights. They've never been anywhere else at 16, 13, 9. They eat one meal out en route and that's it. Their luxury is a big box of magnums and that is as luxurious as it gets. No days out. They pay £350 for the 5 nights. Like the other friends they view spending on holidays as a waste. They can't see why people spend even 1k on holidays.
Then I have a friend who holidays 4-6x a year but they won't pay for childcare (this causes serious issues - expectation on family) and no activities for their dc that cost, always telling the dc/school they can't afford it. They go on holiday to mainland Europe 2x a year, skiing in US 1x a year, Florida 1x a year and many weekends away - Dublin, NY, Chicago, Paris etc. They pay the minimum on their mortgage, preferring the longest term possible. Both work FT, husband is a workaholic and not only works full time but takes side jobs - has worked 6/7 days a week the whole time I've known them which is 15+ years. One of their dc would benefit from specialist tutoring and they just won't do it. For them holidays are the spending goal. Similarly we have a family member who holidays at Disney four times a year and a cruise every Christmas. While their dc has a significant disability that many parents pay support privately for, they won't. All their money goes on holidays. They've stayed in their same starter home, don't do renovations, haven't decorated in 10+ years and run their cars to the ground.
The two families I know who do two week UK holidays in Devon/Cornwall both budget 3k/week. One is a family of 4 and the other a family of 5. They find cottages near the seaside and seem to make it work. I would say they choose places with amenities and aren't eating out daily. They spend their time at the seaside, one proper day out to an attraction, a meal out a week and the rest of the time it's the beach or the communal pool at one of the properties etc. It's possible, I've seen holiday photos for both from last year and they had lovely holidays with good accommodation.
I'd not make the same financial decisions as any of my friend or family members I mentioned. We have different priorities and for me it's about balance. I don't view holidays as a waste, it's important to me that dc are exposed to art, culture, history and that we have time to relax and decompress. But I'd never spend what my friend and family member who travel 6 ish times a year do, not even if I was wealthy. For me it's excessive and too focused on one thing and for me any academic or health supports for my dc need to come first. I don't think anyone I mentioned is wrong. It's just that we all value different things.