If you have normal 220VAC single phase (1 neutral and 2 lines, for 220 volts across the 2 lines and 110 between each line and Neutral), then some of the new Variable Frequency Drives will convert the 110 to 220 (208) three phase. About $150 for a 1-2HP motor. worth a look.Depends on where the cost/benefit ratio sorts it's self out in the hobby market. A half decade or more ago I was very interested in getting one. There was no way I could afford to buy one and looked at the DIY side. From my research the pressure not only determines the cut rate/quality, but there is a non linear curve that relates pressure and abrasive use.
If someone is really interested in this type of DIY look at the used industrial market. I came R E A L L Y close to buying a used, but rebuild-able, 20 Hp intensifier unit for about a fifth of the asking price for the Wazer.
If I had 3 phase at my shop...........
Flexible plumbing for 50KPSI is also expensive. I'd expect to see the hobby jets develop along the lines of fixed head and movable work piece. That takes up more floor space but might turn out to be the best compromise?