I purchased the components for our PV well pump from Backwoods
Solar.
http://www.backwoodssolar.com/
Cost of panels, pump, pipe and wire was $1800. This was for a small, slow pump to pump into a storage tank. The bigger the tank, the more you'll be able to irrigate. Tanks are moderately expensive. We still need to have a stand built for the PV panels and will probably get a new pressure tank and a booster pump (you won't need these unless you need pressurized water), so there are a few additional expenses, but we hope to install the pump ourselves. If you hire someone to do the work, labor will probably be the most expensive part, expect it to at least double the cost.