i was a bit worried about the high prices too, but in the end i've decided it's totally worth it.. not only is it a million times safer than travelling alone, they totally cover your insurance for everything that might happen, it's super organized, they do everything for you, they train you, tell you what to do in case of evergency, there are people in the organization you can contact in every country, they send you tons of information about the places you're staying at, give you food, transportation, and a place to stay.. in your stay they include language lessons and i'm also getting to attend lectures about local environment topics..
the most similar program that i found in my university cost twice as much and it was only 2 weeks, and i'm staying 3 months. so i think i couldn't have made a better choice. and considering how dangerous it is for women to travel alone in most of these areas, i don't think i'd even ever have the opportunity to do this if it wasn't through i-to-i. but i guess that it depends on your priorities whether it's worth it or not.