Most costs tend to arise from the cabling, not from the active components, so I would first look independently of the manufacturer at which components best meet your requirements.
The price will probably go down due to a new building regulation that specifies new distance requirements to the property boundary. (3.7m!) The regulation now affects people in the new development area who acquired the land through the lottery procedure and who now want/wanted to start the construction project.
Yes, it then has to be compulsory since on one side we only have 3.15m to the neighboring property.. On the other side we happen to be exactly at 3.70m. Plus the dormer which probably is not allowed to be built as drawn..