I don't want to clutter the OP's excellent thread (or over-shadow all the compliments rolling in about chicago's girlfriend ) so I respectfully won't post after this.
Expensive compared to what? For large deployment, the difference in price versus off-the-shelf ATX PSU's (even without factoring in the higher efficiency rating) is huge. You can buy a 2880W PSU, breakout board and cables for less than 1 EVGA 1300W G2, and have higher efficiency rating (as well as over 2x the power). If you mean they are expensive versus wiring it up yourself, I personally think they are good value. I have modified MANY smaller 1 kW DPS 800GBA PSU's in the past, and it was at least an hour of work per PSU (with only 4x PCI cables per PSU, not 20+). With 3,000 Watts of AC power, if you go without a PCB you have some serious soldering to do. If you do get your own PCB made up (and essentially your own breakout board), you have to source out the proprietary connectors, which at this point J4bberwock has been waiting on for around 2 months at the factory. They are not cheap, but they do represent a lot of value IMO.
/shameless plugs
Well, for the psu I'm buying, I found the connectors in Canada for $10 a piece. Was quick.
But I can se the plus and minus to the boards. I may still jump and buy 10, but it's a large chunk on my ROI list.