Not applicable. The Mythical Man-Month says that if you have a library of 10 functions, getting 10 people to work on it will not get it done 10x faster than having one person work on it. If you have a team of three where one person does A/B UI testing, the second fixes memory leaks in the data storage backend, and the third sends bills to the customers and goes golfing with potential clients, well... that's not what the Mythical Man-Month is talking about. That's simply a well-run business.
Having multiple developers and a manager means the project is going to get bogged down in meetings and communication.
Sure, he may be slightly cheaper than hiring a UI guy and a backend guy and a product manager, but I bet he's actually faster, too (at least in some situations).