[htag]

Labour: Having people climb around roofs is dangerous, and people with dangerous work expect higher compensation.

Inverter: Cost of materials, assembly, and QA. You want good stuff for the amount of current passing through.

Cabling: Cabling is mostly materials in cost. Conductive metals are expensive.

Metal Mounting: It's heavy, and requires lots of raw material and expensive equipment to create it.

[nocoiner]

But presumably it’s cheaper for the average HN reader to hire a skilled tradesman to do the install than to take the, say, 2% chance of a debilitating fall from the roof?