Some stores have 30 day price guarantees, others 15.
I was one of those who purchased only a few days before the price drop. (Ordered Tuesday night at 9:30pm via web site, saw the price drop after 10:30pm Thursday night, phone was already on FedEx truck with delivery ETA of Friday.).
When I called Moto Thursday night upon seeing the price difference, I found Moto apparently doesn't seem to have a price guarantee policy. They said they did not have a way to refund the difference to my card. The rep offered me a $100 google card, but not sure if that was right, because later they offered me $100 in accessories. My other option was to return the phone and reorder one at the lower price. I asked for a supervisor. The supervisor gave the same options, and was going to look into other options and call me back. Friday when I called back to check, not waiting for the supervisor, the rep offered me a $100 visa gift card. I took it. When the supervisor called me back, it was accessories or the Visa gift card. I took the Visa Card.
If you purchased your Dev X weeks ago, or longer, I wouldn't expect Moto to do anything. If you got it a few days before the price drop, yup. Then again, where is that cut off? 3 days? 5 days? two weeks? If you are less than 30 days, its worth calling I doubt they'll offer you anything unless you ordered a couple days before the price drop.