Lil.Disney.Princess is from the UK, and I suspect she isn't kidding.
The cost situation for UK parents is much more an issue than it is in the US, because the school schedule in the UK is nationally mandated. Almost every school in the entire country has their "holidays" at the same time. Most UK families vacation outside the country, and almost always take package vacations for their trips. It is not unheard of for UK tour operators to boost package prices as much as 500% during the nationwide school holidays, especially to destinations which are popular with families. As their trips often last for nearly a month at a time, that REALLY adds up. Her sentiment is not unusual, and the topic comes up in news stories quite often; the UK government has even accused the travel industry of illegal price-fixing on a few occasions.
Most UK schoolchildren do not have the long summer break that American students do; while it is their longest break, it is usually only about 6 weeks, not 12, so even travelling in summer does not do much to help their families avoid the peak holiday prices.