Low-end MBP 15" with high-res screen: $1900
High-end MBP 15" with high-res screen: $2300
Put AMD HD 6900M, makes it $3000, makes MBP thicker for heat dissipation. Decreases battery life to 5 hours on IGP, 1 hour on GPU.
Put 12.7mm Blu-ray drive for gaming, makes it $3300. Even thicker and heavier.
4 slots of RAM and RAM bump to 8GB, raises cost to $3500.
Slap a 1TB 7200RPM HDD or 256GB SSD for performance, raises cost to $3700/$4000 respectively.
If Apple was to make a gaming laptop, the above WOULD NOT be a BTO laptop.
Which would you rather get: A decent MBP that can play most games at decent graphics level, which costs $2000
Or, a decked out MBP that can play games at a uselessly high detail level, which costs $4000?
Or, an Alienware for $1500, which you can easily hackintosh?
Your choice.