Assume, for a moment, you want to get high. And you want to do it on the cheap.
For around $300, you can drive to Massachusetts, pick up an ounce (about $200), and drive back. For $450, you can even hop on a flight to Denver, buy an ounce (about $40) and fly back.
There are flaws with these plans. After all, it's still a felony to transport even legally-purchased cannabis across state lines, even between states that allow it.
But if cost is the main concern? It's cheaper than buying legal weed at most dispensaries in New Jersey.