I think the price they're offering it at is pretty terrible - he should be able to get that board made and populated in China for £5-£10. That plus copying a bit of software on to an SD card ... doesn't seem right to profit so much from open source software.

Also, the board doesn't need the opto-couplers for the stepper drivers almost everyone uses, as they're already isolated. Remove those and the cost is now well below a fiver.