But you already go through the exercise; you compare the cost of adding a server versus the cost of engineering a solution. The only difference is server cost is different. My time's worth $200/hr, what's yours?
Hence the use of the phrase "extra effort." In a theoretical world where Microsoft offered "Microsoft Map Reduce" as a Microsoft-sanctioned way to run map reduce jobs, one could imagine the licensing cost for a single box could well exceed the cost of hardware, ops, etc, if SQL server license fees are any indication. How much extra engineering effort does this translate into? Is it worth it?