Not one-off, we're building them into a product, but it's low volume.
This unit will require 4, future units more or fewer.
(BTW, another gripe about the descriptions is it's not always clear if the control lines are active low or active high. I was excited about http://www.dx.com/p/arduino-compatible-8-channel-24v-relay-module-expansion-board-145731 but that's not clear, and of course, it's out of stock.)