Who pays your child's education then? I take it he or she goes to tax subsidised state school, funded by the taxpayer.
You can't blame the travel agents - you try booking direct and see if you can get flights and accommodation any cheaper. Don't forget many hotels and self catering complexes put on extra activities for children during school holidays. At the complex I stay at, a lifeguard is provided for 12 hours a day, 7 days a week during peak season, the pool is closed during low season, as an example.
You are teaching your kids that it is acceptable to break the rules. You need to teach them that if there isn't the money for it, they can't have it. I'm sure school trips abroad are cultural, educational and relatively cheap.
Single people often have to pay a hefty supplement if they holiday alone at any time of the year. Should the government intervene on their behalf too? I can't see what the government can do about the cost of foreign holidays anyway.
Holidays are luxuries.