There used to be an Open-Source project called Ming, which was exactly that... a library that would generate Flash based on C/C++. I'm not sure if it ever got anywhere, though.
As you can imagine, the most efficient ActionScript code is going to be generated by you, writing ActionScript.
$1700 is way too high, especially if it's only running a 9800 and an AMD processor... I recently built a Core 2 Quad 2.8Ghz with a GeForce GTX 280 for $1600, similarly specced otherwise... (except the hard drive... 160GB? what?)
For this... I'd say around $600-700.