There's an impressive cost escalator on size... and I honestly can't see how its justified. Each sized machine is essentially just a bit more box-section/rail/screw and not much else.

Anyway, what is curious to me is the choice to orientate the gantry to straddle the widest axis... Is that a good thing? (it feels like you're creating a problem with an unsupportable beam... if deflection was a concern)