Unfortunately (for you), some engineers are just better than others. The right engineers on your team can make or break your company. It can mean the difference between being first to market with innovative game changing solutions, or putting out a shitty product filled with defects and poor design choices.
And experience has consistently shown that the best engineers tend to be American or American educated.
So yea, you can hug your fantastic offshore engineers tightly and treasure them. But the fact is if they are as good as you say, they should easily be commanding higher salaries that justify the kind of ROI they bring to a company. Why go cheap on the salary for an engineer who could 10x your revenue? If they're not being paid those high salaries, then you're exploiting them. And worse: they can easily be poached by competitors who offer to pay them twice as much as you, leaving you with the problem of finding new hires again.