I don't want to speak for Ryan here, but you're probably going to get a partial refund on those prices. Those prices are for worst-case scenarios: if the volume from your group buy is very low, then that price will be the manufacturing cost. But this group buy already has decent volume with Stumptown, so the true price is unlikely to end up being that high.

Keep in mind, also, that Stumptown will send for manufacture upon receipt from each individual group buy. If you see lower prices elsewhere, it may be because they're going to wait for ALL of the group buys to come in before sending out. That waiting period may easily cost you more in Bitcoins mined than you would have spent to get them done faster with Stumptown.