That line of argument require there to be a line of competent and productive 3rd world developers ready outside the doors of Mozilla HQ. Not just productive developers either, they'd have to be entirely intrinsically motivated and self driven, preferably with projects lined up. They would of course also have to be completely at-will, at risk of being terminated after their quarter year contract. Anything less than that will cost more then the developer salary.
My argument, more directly, is that a developer is not just a salary. You need support staff, office space, capital, and actual work for them to do. You need to hire, manage, and tutor them. Comparing developer salaries to money spent on one-time goodwill activities is ridiculous. Internal billing at enterprise corps usually estimate two times salary for "real cost", but that still assumes you're actually holding that cost against a tangible planned project.
My argument, more directly, is that a developer is not just a salary. You need support staff, office space, capital, and actual work for them to do. You need to hire, manage, and tutor them. Comparing developer salaries to money spent on one-time goodwill activities is ridiculous. Internal billing at enterprise corps usually estimate two times salary for "real cost", but that still assumes you're actually holding that cost against a tangible planned project.