The headline of the article in the Monday Morning edition of the Boston Herald for June 4, 1884, called it "A magnificent structure costing $3,000,000." Coming at a time of widespread depression, this must have seemed an astronomical amount.

The original loan authorized by the legislature for the cost of construction was $2,500,000, which was in addition to the cost of the land, valued at $1,650,000. According to the informative 1895 King's How to See Boston, the eventual cost of the project amounted to $3,828,000.[1] The exact amount of the cost was published in The City Government of Boston by the outgoing Mayor Nathan Matthews, Jr. He wrote that the cost for the Suffolk County Court House, including the site and furnishings, was $3,828,601.80. [2]

Footnotes
[1] MOSES KING, KING'S HOW TO SEE BOSTON 12 (Boston, Moses King, 1895).
[2] NATHAN MATTHEWS, JR., THE CITY GOVERNMENT OF BOSTON 73 (Boston, Rockwell and Churchill, 1895).

Legal Tender/United States Notes Series 1880