now, deduct from the total the value of the "fun" ..
... the volunteers gained and your total will be negative.
Really, the people who did this work are volunteers. They chose to spend their own time in this pursuit and therefore gained some (intangible) benefits from doing so. Whether that was entertainment, peer-group recognition, bragging rights, magnanimous giving, the chance for fame or self-education is irrelevant:, what they got out of the exercise was, as a whole, greater than what they put in.
So far as corporately sponsored or produced donations goes - who can say. In true capitalist traditions some choose to give away, or sell at a loss. Whether they get any long-tern gain from that is part of the gamble. Since wealth is increasing over the long-term, you've got to say that this strategy, too, pays off.
By trying to put a cash value on the development effort, the researcher betrays a mean spirited attitude: that everything can (should?) be thought of purely in monetary terms. By assuming the costs are all in US dollars and includes american rates of overhead (the 2.4 times salary component) he/she/it demonstrates a level of parochialism that invalidates not only their attitude, but their methodology, too. Ignore.