I can't say that I agree with your numbers. Using Cannondale (my new love) for example, the lowest end mountain bike they sell is $550. Like cellphones, computers, motorcycles, watches, etc, you don't want the lowest end. The bikes a beginning mountain biker should consider start at $1389.
The serious mountain bike line starts at $4k and goes to $10k.
Cheers!
I'll have to tell you sometime of how I got my Cannondale "hybrid" and how my son literally ripped the cranks off of his mountain bike.
Cheers!