I could get behind some kind of "perk" for participating in the group buy like this.
https://bitcointalk.org/index.php?topic=195004.0After shipping we do not refund, but still guarantee a six-month warranty of free replacement like our blades. However the replacement should also come in batch (10 at one time).
The extra 19 aren't perk units, the retail 1.99 BTC price includes a 6 month warranty as per above. I wouldn't expect to get back used equipment after exercising a warranty return. If he is going to mine with the groups warranty units and keep the profits in addition to his original payment great, but it would be in good form to throw something back to the group.