This was discussed at length some time ago, but as far as I've heard the boards are identical. No code variations, no hardware changes, nada.
Also, regular Zelda carts go for more than $10 with nominal regularity. So c'mon, be reasonable
. I'm with Mark on this one, it's probably in the $300 ballpark, but I haven't seen one in a while (not that I too actively look), so maybe somebody will get a bit jumpy and go overboard. I think the $600 BIN is REALLY optimistic, though. These peaked a while back, and I'd say a mint one would be $500-ish nowadays.