I dont like to use this analogy because its simply not true. I prefer talking about work ethics. Even though it is rare, we have great devs that even after getting insane amounts of funds, they still keep pumping out good quality content. This is not a reason, it is personal.Here is only one reason why he so slow:
A bunch of idiots are already giving him money, what's the point of investing in work every month if you can do it once every six months and get the same amount?
Stop sending him money and you see how fast he can working.
Edit: But I do agree, if he stops getting the money, he will probably speed up the development, you are right.