Nothing against non-residents, sure they are smart, and I know that many engineering grad programs have over 50% NrA’s for grad students, but why is Northeastern’s percentage 20-30% higher than competitive engineering schools? 6% is really a tiny percentage of domestic grad students.
(Source data: profiles-dot-asee-dot-org)
Northeastern is very undergraduate-focused, and masters degrees in CS/Engineering are typically used these days as ways to validate degrees from international students with bachelors degrees from schools not known in the US. Northeastern already has a high international student population for various reasons even at the undergraduate level (about 20%), so that higher percentage likely also translates to the MS level. International students tend to be full pay at both levels, which then likely funds the undergraduate level in terms of resources, scholarships, and financial aid. Northeastern has a lower endowment than most schools at a similar level and likely attempts to attract full pay MS students to fund the undergraduate program.
With few exceptions, most universities, in particular STEM programs, do not have the funds to cover their costs. Even Harvard will tell you this and their endowment is north of $37B. Northeastern endowment is about $795M. A lot of money until you look at operating costs. Quite frankly, Northeastern is doing a remarkable management job!