Altcoins being sold off could also be interpreted as an attempt to push up the price of BTC by buying BTC.  The charts show that altcoins were sold for BTC as the BTC losses are high.  We also see flows into Tether and other stable coins as expected. SBD is not included in these flows.

From the look at what is happening it appears that Bitcoin Cash drama has created uncertainty in the market which has spread. At the same time it does not seem sustainable and below are some reasons:

- Mining costs clearly are not sustainable. This could be a normal filtering process where inefficient miners are simply priced out of the market but at $5000 or $4000 BTC isn't likely going to be profitable to mine unless difficulty reduces. Maybe some experienced miners can fill me on but it does not appear profitable.

- On Steem SBD is below $1 and this too is not likely sustainable. I don't think SBD can stay below $1 for very long.

- The cost to run many of the alt chains may reach a point where things become unsustainable. If that is the case then the technology will have to be improved and new incentive structures will have to be tested.