The "I wish I had that" recently was for some custom one off parts for a recumbent tandem trike. The part did exist as a standard manufactured part... in Germany. There is also an online bike shop with no inventory that probably does what you describe... and at that time had a backlog of two weeks.
This was for one part - a custom gear. Yes, a professional machine can do that in no time flat for less than the cost of the Wazer. No, the professional machine can't do that in the same time it takes to make the part and it was actually faster to order from Germany in this case than to try to find time on a professional machine shop somewhere.
Sure, if you're going to make hundreds or thousands of the parts - thats great. But if you want one or two... not so much. Especially if that has the timeframe of "today" on it to fix that gear to go out cycling this afternoon.
Our rush service typically gets parts delivered to the customer within 3 days. Regular orders ship in 7-10 days.
As far as finding a shop that can take your order quickly, try a search for something like "waterjet cutting online ordering".
The Wazer's speed makes it difficult to get a part done in a single afternoon. As I mentioned elsewhere, you'd probably be better off with a small CNC milling machine. But do you really want to own either for only occasional use?
The related question would be "what is your minimum order?' That's where a personal water cutter may work better for some. The occasional use is indeed a question - and how much additional things may be done or prototyped. How many jury-rigged parts are on the trike that could be done better with the proper custom part. And if it's worth doing a one off order for a gear or bracket that is 2"x4".
That minimum order is significantly higher than the price of the part from Germany... even with shipping. And with the gear, one spare isn't that useful... and the parts for the trike ( http://www.terratrike.com/tandem.php ) tend to be a bit specialized - I don't know anyone else who has one (mine is similar though has different parts and such because its a folding http://www.terratrike.com/traveler.php ). In the past, my father has gone to the machine shop where he used to work for custom parts - but the people who he had favors with to get some time for non-academic projects have nearly all retired.
Yes, it is certainly cheaper to have an industrial cutter if you know what you're making and making them in lots that cost a few hundred dollars. If you are after making a part rather than a half dozen... that minimum order and turn around time (do it on Saturday, have it on Sunday?) make it less interesting for some applications.
Latency is a major advantage of this stuff. Do 10 examples on this as you iterate a design then 1,000 on a professional device. Even if it is really slow, you can probably use different materials and or thinner materials.
As other comments pointed out there seems to be an issue with max pressure it can produce. If it has to be run for hours on end it might actually be cheaper to get a local place to do it...(Not even considering the costs of maintenance and consumables, just power and initial price)
I've had parts made on a crappy waterjet once and we just tossed them all out due to extreme taper (Although the company was a massive piece of shit too, used the wrong material)
Given equivalent running costs, this means that 2 hours of runtime on a pro Flow or Omax machine is equal to the price of the entire Wazer.
In other words, the $6000 you spend on the Wazer will buy you a LOT of complete parts from on online service like Big Blue Saw.