The Congressional Research Service his issued a revised “Coast Guard Polar Security Cutter (Polar Icebreaker) Program: Background and Issues for Congress” updated 9 August 2019.
It includes a short appendix (Appendix E, pp 63-66) on the issue of a potential new Great Lakes icebreaker. The final paragraph of that appendix states:
“An examination of procurement costs for Mackinaw, the National Science Foundation’s ice-capable research ship Sikuliaq, new oceanographic research ships being procured for NOAA, and OPCs suggests that a new Mackinaw-sized heavy Great Lakes icebreaker built in a U.S. shipyard might have a design and construction cost between $175 million and $300 million, depending on its exact capabilities and the acquisition strategy employed. The design portion of the ship’s cost might be reduced if Mackinaw’s design or the design of some other existing icebreaker were to be used as the parent design. Depending on the capabilities and other work load of the shipyard selected to build the ship, the construction time for a new heavy Great Lakes icebreaker might be less than that of a new heavy polar icebreaker.”