I don't doubt the price will drop as they become more popular (it's probably a few dollars worth of raw hardware), but right now it's a fairly niche product.

"a campaign where the cost per unit goes down as they reach certain sales goals."

That's an interesting idea. It gives purchasers an incentive to promote the campaign, as opposed to "early bird" specials which incentivises early purchasers, but almost disincentivises later purchasers.

This has been done on Kickstarter and software bundles like MacHeist in the form of "unlocking" additional rewards, but I don't think I've ever seen them actually lower the price if they hit certain goals.

It seems as though this model will merely deter possible buyers. Why would I pay a premium now when I can wait a few days, let others incur the initial, inflated cost, and then purchase my thing at a substantially lower cost?

This phenomenon, where people wait until the last minute to go in on a product, is already pervasive on Kickstarter. (I'm not entirely sure why, but the most obvious reason is that people want to ensure that the project will definitely be funded or will attain some sort of stretch-reward before buying). Dynamic price-lowering will only exacerbate this trend, discourage initial purchases, and likely produce more failed projects.

You got it backwards. Think of a model where you initially commit to pay full price, but everyone gets a discount that increases as sales targets are met. It would be no different than any "refer-a-friend" discount that you see at gym clubs or satellite subscriptions.