Hmmm, a million years ago, I traveled as a Girl Scout. Two memorable trips spring to mind. First one was with my troop through a number of National Parks and historic points of interest to and from National Center West, near Ten Sleep, Wyoming. Awesome trip!
The second was a smaller subset of scouts from multiple troops, who went to "Our Cabana"* in Cuernavaca, Mexico. I was older for this trip, and thus remember more.
The costs were quite low and I know I paid a good chunk of it through babysitting. I'm sure these trips contributed to my love of travel.
Two random stories from the Mexico trip: none of us wanted to wear our uniforms, but one day when it was mandatory, we were amazed at what respect they garnered. The rest of the trip, we all voluntarily wore them. Once, when two of us were separated from the group, we hailed a cab and said "Casa de las Guias". Because of our uniforms, he knew where to go and we were swiftly reunited with our group.
The second story, happened when we were not in uniform, finalized our decision to voluntarily wear them. We were on a crowded subway car (first subway ride for most of us) during rush hour in Mexico City. When we got off the car, one of the girls burst into tears. Seems someone's fingers had been pinching her ass and she froze, rather than speaking out or moving. I said she should have told me, I'd have kicked whoever it was in the nuts for her. Apparently this got back to my mom, who was a chaperone on the trip, but was in another section of the car. I thought I'd get in trouble for saying that, but apparently she was quite pleased. I never understood why the other girl did nothing.
My point is that your kids can make life-long memories, such as mine, in other ways, for a fraction of the cost. Seek out other opportunities if you think your kids will benefit from travel, but not at such a high price.
My current city has a Sister Cities Program with two similar size cities in Europe. The participants come from all the high schools in the city, so the kids get to meet others from the same area, plus make new friends from far away. The trip doesn't have to be with her school.
*I remember it as "Nuestra Cabana" but Google insists on "Our Cabana". Same place.