I don't understand the negativeness. TCG Player has a lot of problems that not a lot of other mtg market websites address. If Deckbox can do a better job at facilitating person to person sales of cards, then I for one am happy to be along for the experimental ride.
It shouldn't take too long for enough data to come through to balance the prices. Rome wasn't built in a day, so they say. Deckbox is my favorite way to inventory cards, so the addition of a market (besides the already robust trading system) seems like a perfect fit. In fact, when I first started using Deckbox, I had expected them to already have something like that in place.