The "makers market" works just fine if you're selling Arduinos from China. The rest, all of it, adafruit, sparkfun, hackaday, supplyframe, tindie, all seem to have been acquired based on user count. I don't think Supplyframe or Siemens has any idea how to monetize them, but maybe there are juicy sales leads to discover in the userbase. Probably not, but you never know.