Just randomly saw this, feeling a bit of Buyers remorse since I bought my second hand TacX Satori (the lower model which has magnetic resistance meaning no ERG mode) a few months ago on Gumtree for $200, this seems like quite a good deal. Had a quick look at a couple of other stores and saw it was still up around the $500 mark.
Hopefully this helps someone
(link to google shopping search for the same product for comparison)
https://www.google.com/search?q=tacx+vortex&safe=off&source=…
Just buy it the sell your old one. Can't lose much if you bought off gumtree initially