True, but I think there are two factors at play:
1. Europeans traditionally create higher demand for manual than Americans, so there are sales numbers to support the cost.
2. I think the American tests are uniquely expensive to perform on manual transmission. Europe may have high standards on emissions and efficiency, but also testing methods that aren't quite so costly for the manufacturers.
At least this is what I've heard, second- or third-hand. I don't work in that industry, so even if accurate, my information may be a little old.