Massachusetts's top marginal state income tax rate is 9%. State tax is progressive here, so most filers pay an effective rate well below the top figure — the calculator applies a blended approximation rather than modeling the full bracket schedule.
A 4% surtax applies to income above roughly $1M. Statewide median household income is $101,000, which is the default loaded above.
Remember that a state with no income tax is not automatically cheaper overall. Massachusetts has an effective property tax rate of 1.04% and average homeowners insurance of $1,700 a year — states without wage income tax typically recover revenue through property or sales taxes.