I can't understand why some people dedicate so much hour into a completely open source project without closing it and yielding greater profit from it.

I don't think profiting from your code is evil, I think it's a great motivator. Why do some people feel that commercial software and generating money from it is bad? There seems to be this black and white thinking that open source = good, commercial = bad. I hardly find this convincing, and often commercial companies which are supported by sales produce very good results. An open source software in the same niche can't compete against the corporation. Of course, sometimes this is completely the other way around where private companies produce inferior product compared to open source counterparts.

So help me understand, why do programmers open source their code when there is commercial prospects for it? Shouldn't the rational programmer or human being make every effort to capitalize on their opportunity cost? Working on a open source project for months when you could've spent the same number of hours at commidity wage or some other monetary compensation?