It is absolutely inappropriate for those who can afford the class trip to be mocking those who cannot afford it. Talk about out of touch!
Let's say 20% of the kids in the school are below the poverty line. Are these kids expecting their parents to give up money to pay rent or the car payment so the child can have the luxury of a trip to Spain?
Another matter to consider are the parents who have some savings but have to choose. Do they put money back for their child's college or pay for the single trip to Spain? As an investment in their child, several thousand dollars towards college tuition is smarter.
These ignorant, elitist children should either figure out how to help more people pay for the trip or shut up.