Has this product even shipped five million units yet?
Apple sold 1.4 Million iPhones total in all of 2007 (so in 6 months). Apple hasn't revealed sales numbers for the Apple Watch yet, but it's estimated that they sold somewhere between 1 and 3 million as of the end of June, after it had been on sale for 3 months.
So the Apple Watch appears to be set to sell somewhere between 2 and 6 million units in the time that it took the iPhone to sell 1.4 million.
What a flop - it's only doing somewhere between 42% and 300% better than the iPhone did.