If the author owns copyright on every line of code used to make the binary, they can do what they like with it without need for a license.
However, if there is other GPLd software in there, and they are relying on the GPL to be able to distribute it, then you are right, they need to comply with the GPL requirement to distribute everything needed to build it (Makefiles etc...).
Even though this is incorrect, I agree that this seems to totally violate the spirit of GPL which is meant to be used with free software. It's one thing to open source your code and have people donate to get support and fund development. It's quite another to charge for binaries. Others can just redistribute your binaries instead of you, so what is the point? Also, you are open sourcing and GPL'ing it, and yet you won't follow through and actually provide the built code- that's just shooting yourself in both feet. But, you have to appreciate the fact that he did open source it and that he is trying to make money off of it.
Sure it is. Under the GPL you are not allowed to distribute a binary without also distributing the source and dependencies. But it is fine to distribute the source code without bundled dependencies.
Certainly. I'm not saying it's a viable business model. As I mentioned elsewhere in this thread, one person could even buy the pre-built binaries and freely redistribute them. The GPL allows this. However the parent is still factually wrong.