Well, I'm seeing this question in the close queue again. Now it has an edit that reads:
The program should be open source, not proprietary. Well at least people should be able to take a look at it.
but that almost goes backwards what he asked earlier:
If I would like to sell my program that is written with Qt and the PyQt4-python-binding, do I have to bother about buying the licenses (3000+300 € or so)?
Or is there a model where I could just pay them (the license owners) a part of my gains? I can't afford those licenses.
Before it was clear what he was asking... now, it isn't too clear...
Looking at the answers my TL;DR is:
Depends of the license, if the license says that you have to pay royalties to sell, then you pay in the way it says, if it doesn't then you don't, but either way look for legal consultant.
Looking at the revisions, not even Mods are clear if it's on-topic or not (just now I discovered that it was closed again -_-, and opened again by Oli). We can play catch all we want with the Close/Open votes, but it shouldn't be like that. Could we take a concise and defined stand for this kind of question. I will propose my solution below as an answer, please don't be afraid and propose yours too. Vote for what you think is more suitable to what AskUbuntu is.