The prevailing wage is the one that you should be getting once you get your GC. So if your current salary is less than the prevailing wage, it's not the problem.
In this case, you company need to show financial ability to pay you minimum of prevailing wage after you get ur GC. This is shown by using ur company's income tax documents which should show that ur company has net income or assets of more than the difference between the prevailing wage and ur current salary.
Say ur current salary: 64,000
Prevailing wage: 72,000
Difference: 8,000
Say ur company net income (net assets): 50,000
Since ur company net income > the difference, ur company has ability to pay you after u get ur GC.