The privately owned museum is celebrating a gala “shipbreaking” ceremony tomorrow to mark the official start of construction at Fort Point Channel, near the place were colonists dressed as Indians tossed heavily taxed British tea into the harbor in 1773. The museum, originally priced at $9 million in 2006, is now estimated at more than $27 million.

The Massachusetts Convention Center Authority, a quasi-public agency, has committed an $18 million low-interest loan. The Boston Redevelopment Authority, also a quasi-public agency, has directed a $3 million grant to the project.

Now, members of the Tea Party’s modern namesake political movement are raising their eyebrows at the financing arrangement.