I'm almost 100% positive that you can never get the  3MH per server. The reason I say this is because the most cost effective card I've ever seen is a 5830 @ $110. That will give you 3 megahash per dollar but becomes diluted the moment you add other costs. You will not find multiple 5830's for less then 110 because it is in such high demand.  Machines like the one deslok bought wont come up on the market very often because he had to find really good deals on the 5770's and a super cheap computer that could handle them.

The max you should expect out of completely new parts is 1.5 megahash per dollar and if you wait to find sweet bargains on craigslist ect expect 1.5-2