$300 to port a game? Jeezus that's cheap. I'd charge like $5,000 at least probably. The standard rate around here is $100/hr.
It was ridiculously cheap, and I think they might have underestimated the work a bit when they took the job. For example they had to rewrite the complete rendering engine because I was just using brain-dead immediate mode rendering which is not supported on Android. I actually felt a bit like I was ripping them off towards the end, but they never complained and finished their job as agreed.
We did agree that a next assignment would be for an hourly instead of a fixed price, which was still cheap (but very reasonable for talent by Chinese standards) and I didn't even have to negotiate on that rate.
I'd still hire them at that rate without hesitation (they're talented, and very nice guys to boot), but you always have to factor in the extra time and effort: Outsourcing is not easy and don't expect to be able to throw your project over the fence and get a perfect product back without putting in the effort to manage things like cultural differences in things like expectations and such.
One thing to remember if you're going to opt for outsourcing: Don't do it only to save money, do it because there's a lot of talent outside of the western world! It already cost me quite some time and effort to find these guys in the first place, but in the end it was a good experience.