I think 500 dollars is too low and 1000 to high I think something in the middle like 700 seems about right but as we know the price of those coins has a tendency to tank, but I think at the beginning is going to trade at very high prices then everyone is going to start to sell their coins and the price is going to go down, however the stable price of the segwit2x coin will depend on how much support it can actually gather since the support has been going down in the last weeks.