Tuition at UMass is 8k+, fees are 5k+. So the combined costs - what you'll find in the MSAR, USNews, whatever - are somewhere around 14k/year. That's as inexpensive as you'll get outside of Texas.
The $42,000 max you can borrow is what the Financial Aid office thinks you'd need to cover all expenses for the year...tuition and fees, plus rent, food, health insurance, gas money, entertainment, etc., etc., etc.
[Actually, I see that fees have gone up, so now the total is between $15 and $16k/year. Still less than the SUNYs or UConn, let alone a private school.]