Have you seen a desktop with 4 quad core xeons or opterons with over 100 GB ram. Or a gaming i7 with nitrogen cooling or fan the size of a bowling ball, running at 4.5 GHz, or 4 full sized video cards. With a 1200W power supply??
What's your point? Both are specialized machines...one is optimized for server workloads and the other to give boners to nerds. While laptops aren't quite a match for high-end consumer desktops, the gap probably isn't significant for the majority of this forums users' needs. Yes, my Core i7 iMac has a faster processor than my Core i7 MBP, but the MPB has an SSD (both of have 8gb of RAM) and it handles all my RAW imports and photo editing much faster. Sure, the iMac would be faster still with an SSD, but my real point is that for the majority of this forum's workload, the difference isn't all that great and depends more on I/O speed than anything else.