Personal anecdote - my house has two sets of solar panels on the roof - the first was installed in 2017, the second was just installed last month. In 2017 my 6kw system cost $24,000 before any incentives (by SolarCity). In 2020 my 7.8kw system cost $15,000 before any incentives (by Tesla). Of that $15k, $4.3k was for the panels themselves, $2k for the inverter, $1k for mounting hardware, and $8k for installation. It'…
I'll add some anecdata from Australia. My neighbour had a 5kW system put on, single-phase inverter, about three years ago - for ~ A$7000. I've just put a deposit down for installation of 12kW of panels with a 10kW three-phase inverter for A$7400 Same provider, though I haven't compared breakdown of costs (I'm assuming very similar installation / labour costs).
Considering a similar system like that in southern Europe where installation is pretty cheap, and the prices are higher, I see A$12000 for a 10KW system of panels and a 10KW Fronius three-phase inverter.