I already addressed that. It's churn due to free trading. Put another way, if NO (as in zero) miners sold any of their coins, do you still think prices would fall?
I called my econ prof, he said, "Yes" and I agree with him.
You see, supply > demand right now, so the price falls.
If supply < demand, the price would rise.
You've made the mistake of assuming the only "supply" of coins is miners. That's not true. The BULK of the supply is actually people who already own coins putting them up for sale.
The 7200 coins per day are not a "significant" supply to the market. The other 105,000 coins being offered for sale ARE. So even if the miners' coins were gone, the price would still fall, because people aren't buying coins for what sellers are currently asking. As evidenced by the MUCH larger trading volume.
Now, if the trading volume in a day was just the 7200 coins for that day, you'd have a point. Since it's 16X that, you don't.