(Not specifically pointed at Huw, just taking your post as an example to hopefully emphasize my point)
I feel its a pretty big lack of recognition for those having worked on GTA5.
Yes, its the fifth game in the series, however the series spans several generations of hardware. I agree with your reasoning if it were Madden, Fifa or CoD, but the time in between releases of the various GTA games have been quite long.
Rockstar only charges people for extra money in GTA Online, which arguably is a different game entirely from GTA story mode.
And besides that, you aren't locked out of content from GTA Online if you don't pay. Its cosmetics or shortcuts as far as I know, so people pay voluntarily and that happens to make them a good chunck of cash. A different intention of creating something if you ask me.
Do you think Digital Extremes would keep Warframe running if they didn't make a good chunk of cash on it? Of course not. But that doesn't invalidate the fact that Warframe IS a labour of love for the studio, as you have seen in the documentary on YT. They kept on trying to make THEIR space ninja game and finally succeeded after years of hitting walls, fumbled deals and no interest from various parties.
Yet now the project has grown so much (and people need to eat and pay bills) that the fact of the matter is that they need to keep making money off of the game. Is there a point where Warframe then ceases being a labour of love? I don't think so.