As my daughter pointed out, attention to the details of Harry Potter's world is also patchy. (1) As everybody knows, the Gryffindor Quidditch team includes several girls. As far as we could tell, all the players in this game are represented as boys. That is a huge demerit for this father of a daughter.
Pricing for Solar Photovoltaic (PV) Systems. Generally, Solar PV systems that generate electricity from sunlight cost between $1.95 to $6 per installed watt. Typically, the larger the system, the lower price per watt. Large commercial systems are typically well below $3 per watt. Residential systems, because of their smaller size are usually somewhat higher.
Photovoltaic prices have fallen from $76.67 per watt in 1977 to nearly $0.23 per watt in August 2017, for crystalline silicon solar cells. This is seen as evidence supporting Swanson's law, which states that solar cell prices fall 20% for every doubling of cumulative shipments.