Anyone have sales figures for Steam Machine and how long Valve supported it?
Valve didn't produce or sell Steam Machines directly. They offered just a template that several hardware manufacturers used, sometime with significant variations (i.e. some models came with Windows and Steam preinstalled rather then the Steam OS). There was also very little uniformity in terms of prices.
I guess that would make sales number a bit hard to track, but I doubt any specific model could claim to have been a smashing hit.
How long did Valve support them? Depending on how you look at it you can argue both "Very shortly" and "They never stopped supporting them".
There weren't additional attempts to release Steam Machines after the first launch, but everything they started there only improved over the years (i.e. Proton has improved massively over time in terms of performances, compatibility and reliability, the attempt to support the Steam controller turned into Steam Input that as an API supports basically any peripheral in existence with sticks, buttons and shit, the in-home streaming support became a software framework that now you can use with pretty much any phone, tablet, PC, etc.