so that is producing about 3.5 million new HZ per day as I interpret it?.. seems like a lot.
No, it's a static 1,000,000 per day right now.
Subject to change.
Perspective:
Viacoin miners dump 18,000 coins per day. From December 2014 to February 2015, average price of Via was 9,800 satoshis. That's 1.764 BTC worth per day.
Currently, Horizon nodes may be dumping 1,000,000 coins per day. At current price of 120 satoshis, that's only 1.2 BTC per day.
And Horizon is about to release something innovating.
1.2 BTC per day is good profit if you're the only node. But you have to share the bounty with other nodes. At these prices, you're still wasting electricity if you're selling right away.
The node distribution system (amount per day) was also adjusted in the past, and that lessened the selling pressure quite a bit. I think it is about right now, but of course subject to change if need be.