Actually the selling time version is not really accurate either. What you're selling is the product of your time and skill. And if you substitute "income" for "

Actually the selling time version is not really accurate either. What you're selling is the product of your time and skill. And if you substitute "income" for "part of the income," well, the grandparent's phrasing is an accurate description of what is happening (in that no part of the description is untrue). You my prefer to emphasize a different set of facts, but that doesn't mean you get to say a true thing is not true.