W. H. Heydt wrote:When you say "switch" you mean the light switch? You can't wire power from the switch box. Assuming it's a standard--small--junction box. Why not replace the switch with a switch-and-outlet module that fits in the same space?
I'm not sure how US systems are wired, but usually it is poor practice to mix lighting and power (sockets) on the same circuit. Fine if only a Pi is plugged in, tricky when something beefier gets substituted. Lighting circuits are not designed for power distribution. Also, there is a way of wiring light switches, widely used in Europe, which means that only the line ("hot") side of the supply appears at the switch, so a socket cannot be connected.
While I would be investigating the "compliance reasons" for not having power sockets in the closets (which is something I have not come across in the UK), and also the apparently extreme quote for socket installation, this does seem one case in which POE is a reasonable solution. As long as a nearby outlet can source power to a spare network point, the cabling is all in place and power can be extracted in the closet. It does mean that there is something else, somewhere else to go wrong, but it is likely to be more reliable than attempting to get power from fluorescent lights via solar panels (64W in, light output a fraction of that (25%?), light captured a fraction, probably <1%, conversion efficiency <10%, power output negligible, less than a Pi needs) or non-contact induction (extracting sufficient power could adversely affect the downstream load.)
Just consider, if any such technique could work, it would be at least as widely available as POE.