If you qualify for a subsidy
the Massachusetts Health Connector is the most affordable coverage available, full stop. Medicaid is expanded (MassHealth) in Massachusetts.
If you don't
Full-price marketplace plans are the most expensive coverage in Massachusetts. For healthy people, private PPOs on Cigna, Aetna and PHCS PPO are routinely 30–50% less. Massachusetts has its own individual mandate: adults must carry coverage that meets the state's minimum creditable coverage standard or owe a penalty on their state return.
What's not affordable
Health-sharing ministries and indemnity plans look cheap until you have a claim. Ask for the out-of-pocket maximum; if there isn't one, it isn't insurance.
Massachusetts is one of the most tightly regulated individual markets in the country: the state mandate requires coverage that meets minimum creditable coverage rules, and many non-ACA plans don't. Private options here are narrower than in most states, so the honest answer is usually a careful comparison, not a promise of savings.