Does this mean that you would prefer to get the total cost of attendance down to $20,000/year? Does this include travel?
Have you run the NPC on Tufts, Barnard, and the other private universities on your list? You are very likely to either need help from your parents, or to just have your parents run the NPCs.
I think that you chances of admissions to U.Mass are pretty good. I think that the chances of getting the total cost of attendance down to $20,000/year as an out of state student are not good at all.
I hope that UC Boulder is also on your longer list, or Colorado State, or both. They are both very good universities. You are also from a WUE state and might want to see if any WUE schools are attractive to you. Edit: I forgot Colorado School of Mines, which is also an excellent choice that you should consider and very likely should apply to. You have some great choices in-state.