The ProtoMAX is pretty cool - it's a real abrasive waterjet, operating at 30,000 psi, which makes a good, efficient cut in plastics, glass, stone and most other non-metal candidates for waterjet cutting. I've spent enough time operating a different OMAX in the the same pressure ranges cutting plastics, art glass, tile, foam to believe it's a good deal for someone who wants to cut metals up to ~1/4", and non-metals, and whose needs are met by the 12x12" work envelope. Would sure appeal to more folks with a larger envelope.
We mostly cut metal, but for non-metals instead of piercing low and cutting high, I like to both pierce and cut at a mid-range pressure of 25 to 30K, for good cut performance with most of the damage-reducing benefit of the low pressure pierce, and avoiding the rather severe UHP plumbing fatigue that comes from piercing at a lower pressure.
Cutting metals at 30,000 psi, there's more taper and drift vs. cutting at 50,000 psi or higher, and the cut performance and in particular the abrasive usage is exponentially less efficient, but 30,000 psi is perfectly capable of making good sheet metal parts with reasonable abrasive cost in absolute terms.
Unlike for example the Wazer, with a lower operating pressure that is so inefficient cutting metal, it would cost more in abrasive alone than to just pay a waterjet shop to make a typical metal part. At least that's what I inferred from their web site some time ago.