DAC is an order of magnitude cheaper than optical and might be fine for their use based on their comments of cat6 v cat6a and "short runs in their lab".
Also, if they are using two or three NICs per box, you'd need to factor in the cost of two / three of the X540's vs. a single 40gbe connection and you'd need to double the cost-per-port of the switch vs the 40gbe option.
Also, if they are using two or three NICs per box, you'd need to factor in the cost of two / three of the X540's vs. a single 40gbe connection and you'd need to double the cost-per-port of the switch vs the 40gbe option.