If you kept one Hawk in hand, and then recast it, you would get two more Hawks, and thus one Hawk and Jace would give you a net of SIX total cards
You'll find the full developer post over at the official website, but if you're looking for the short version, here's a couple of choice quotes: "To affirm what we talked about back in September, a smarter system that provides what we have dubbed "duplicate protection" is still our top contender, and the current design space we're working with." "Okay, so we have the goals we want to accomplish, we have the problem space, and we have a system that will help us reach these goals
The problem, for a long time, was that the alternate cost of sacrificing three creatures was actually a benefit, creating multiple Zombies via Bridge from Below
Usually just over $3, its a budget-friendly enchantment that ensures long-term staying power