PS Audio Directstream Dac so many for sale?

It is being discontinued and replaced by a mk2 version. 
The latest Sunlight firmware release was announced as the final update for DSD and DSJ. 

The new mk2 (release date unspecified but probably not this year) has different fpga’s and some other hardware upgrades. See PSA forums for all the specifics

Actually latest speculation is that mk2 won’t cost much more than DSD, but will not include a bridge option so external streamer will be required (mk2 not a one box streaming system).

Like any component that gets replaced, sure there will be deals to be had on the old technology. It’s like a seven year old dac, isn’t it? In dac years that’s pretty ancient. But yeah, probably good value. 

Depending on what you mean by “cost a fortune” you may be confusing the mk2 with the TSS, a product now on long term hold it seems (meaning at least a year likely longer out), which is likely to cost much more than DSD or mk2

But Paul's predictions on release dates are notoriously awful.  Let's see.