Sure the price looks enticing but but it's not a good match.
They use a smaller motor for the Z which would benefit a cnc router but not a mill.
If you can't spend the money for the 6050's or Geckos, look at the cheap Keling packages.
Versus the Probotix, it's bipolar vs unipolar, it's 36V vs 24V and the motors are bigger for $20 more.
Not as good as what been suggested in the past (gecko) just better than the Probotix.