[oil pan 4]

Name brand grid tie inverters are cheap, like 10 cents a watt for multi kw units.
My outback sunny boy secure power supply is more like 30 cents a watt, depending on what size I get. Idk having all those solar panels and not being able to use any of the power being made by the solar panels when the power goes out seems dumb.
Mounting costs are totally dependent on your roof.
If you have a semi ideal roof, metal roof pointed south at a decent angle like I have, racking will cost almost nothing.
Single axis mounts add up to 20%, maybe up to 50%, but that's comparing panel mounts to really cheap 50 cent a watt panels.
2 axis mounts could double the cost.

On a terracotta roof, mounting is probably going to be the majority of the cost.

I'm going with huge panels, at least 325 watt. I saw some 470 watt panels I like.

There are so many panels at so many price points, you have "12v panels" which are small and cost around $1 a watt typically, they could use these panels as your example.
Small 100 panels are going to need a crap load of hard ware compared to the same power coming from 470w panels.

But know this, hardware and material costs like mounts, wire, conduit, batteries, fuel for a generator and labor always go up. Electronics, solar panels, charge controllers, inverters have been going down.