750k is not inconceivable. What is inconceivable is that a significant portion of those "coins" were highly liquid. I agree that if the numbers are that high, it is largely in part due to the use of Gox as a web wallet. The fact that Gox was an exchange is not evidence in and of itself that all coins held there were readily available on the market. Just take a look at the order books -- it puts things in perspective.
If only a smaller fraction of these coins were liquid (say, 100k), then the remaining 650k were for holding, presumably using Gox as a wallet.
Now these holders are no longer holding. So I would imagine that some of them would purchase new coins to replace the ones they thought they had. If we imagine that even 20% would be replaced with new purchases, then this represents an additional demand for 130k coins.
Do you agree?
Specifics are very difficult, but generally, sure. Now the question is how that is mitigated by the latter two points I raised earlier. This doesn't happen in a vacuum.