Never used one personally but I have seen the local water authority use very very expensive equipment and fail miserably with it, so my advice would be to hire the stuff a few times and pass the cost onto the job. That way you will see if it is worthy of the cost before you invest.
I would say that for most expensive tech to be fair.
Things like threading machines, flushing machines, core drills etc etc, are pretty certain purchases, in so much as you know exactly what you're buying, why you're buying it and that they will perform the task you're aiming at, mainly, making your life easier.
Tech stuff is 'fancy promise the earth gadget time' and very expensive if it is useless and doesn't pay for itself. It can look very professional but at the end of the day, you will still need a spade, ear muffs and and a jack hammer.
Is this a real job? are we on UFH?