Average national salary in the US $60k [1] vs 5k for turkey so closer to 11-12x (the coasts typically pay closer to 70k). So at most unions are costing US built ships to be twice as expensive due to unions and overall higher US wages are responsible for the price difference - difficult to compete on price with people that are willing to work for 1/10th your wage unless you can automate significantly more than them.

[1]: https://www.usatoday.com/money/blueprint/business/hr-payroll...