I would have a good reputable irrigation company install an efficient system for you. More than likely with a price varying so much their was a big difference in the quality of sytem designed. A good quality irrigation system will save you tens of thousands of gallons of water over an ineffecient system, and even more over using a hose end sprayer or sprinkler. If you get a good company who knows how to design, then the water savings should pay for the irrigation system within a few years.
Why do people not respect us as they do other tradesmen? Because every Tom, Dick, and Harry doesn't think he can be a plumber or electrician!