Lawrence Berkeley National Laboratory (LBL) has published a interesting report on the 2017 prices of installed PV systems.
The report can be downloaded from LBV:http://trackingthesun.lbl.gov or if that becomes unavailable, from the Arizona Solar Center at: tracking_the_sun_2018_edition_final_0.pdf
Some of the highlights are:
Arizona has some interesting data in comparison to other states. Note: TPO=third-party owned.