The fibre and sfps are a tiny price of the entire solution

DACs will be cheaper than fibre in a bay, but between neighbouring bays about the same.

A 7m passive 40g qsfp dac is £80. A pair of multimode 40g is £66 and 7m multimode cable is £10.

A 2m dac is £28, so fibre is 3 times the price.