Feel free to correct me but I believe the 500k mark for PS3 games has a lot to do with programming for the system being more complicated for the Xbox360. If this was the case it would mean you would need both more experienced programmers for the system and most likely more of them working on the game than you would for the 360 meaning your spending more to produce the game than you would on other systems thus necesitating higher sales numbers. As for a game like RR7 needing to sell 500k to make a profit I believe the game has elements such as cars and tracks that are cross overs from RR6 but I don't think the game is a complete port as extras have been added and it is as has been said that it is in 1080p. One last thing to you have a referance for the 2 month development on Gundam Mussou just sounds doubtful.
One thing that is mostly ignored during X360/PS3 debates is the difference between the companies. Not only is the PS3 architecture much more difficult to program for by nature, but Sony is also a hardware company while MS is a software company.
Naturally, the PS3 is rock-solid. This is Sony's background. They make machines, and largely make them very well. The X360 has its problems in the quality assurance department. MS is not typically a hardware manufacturer and they're basically teething on the market right now. The hardware specs are fine but the quality of the hardware construction is questionable at best.
Inversely, read a few interviews by independent developers and they, without fail, will say that Microsoft provides developer tools that far surpass anything ever offered by Sony. It's a strongpoint for MS while it's a weak point for Sony. MS has decades of experience on how to provide tools to third party developers on their platforms.
I think this sums up the current market right now. Consumers balk at the X360 because they have been prone to failure. Developers balk at the PS3 because the 360 is cheaper and easier to develop games for. MS also provides much more help should you ever run into problems with development. It's their specialty. I've heard of multiple developers saying that they ran into problems on the 360, called MS, and had a rep immediately help them start solving the problem. I've never heard anything like that from a developer on a Sony platform.
I'm not touting one company over another, they're just very different and they come from very different backgrounds. Each has their strengths and weaknesses.