£4k on holidays might not be so out there. It's about what a package holiday for a family of 4 costs in the school holidays. Many people have that sort of holiday. Abta say that at least half of people do, they won't all cost £4k, some will spend less, some a lot more.
www.abta.com/industry-zone/reports-and-publications/abta-holiday-habits-reports/holiday-habits-report-2019
But the point is that many people (probably at least 60-80%) have sufficient disposable income to cope with the higher energy bills, but for most of them, it will come at significant detriment to their discretionary spending, as they see a comfortable disposable income reduced to little or nothing after housing and essential bills, food, travel, clothes.
So they have to reduce or cut out their spending on holidays, extra clothes, grooming, food and drink out of the house, technology, car replacement, decorating/improving their homes, days out, anything that is not essential, but nice to have.
Most people (by which I mean more than half, maybe up to about 70/80%, obviously acknowledging that a significant minority of people have insufficient income to cover even the basics) will still be able to afford the basics, but the lifestyle they are used to will be significantly affected. That doesn't mean that they 'can't manage' higher energy bills. They can, but it's a much less comfortable version of managing than they're used to.