

15k for several distinct hotspots in a city is pretty reasonable, depending on what equipment they are using.
Enterprise quality IT gear is expensive. Each access point can easily be 1k, and that excludes any routers/firewall/switching that you may need at each site. As an example, I’ve worked in places that had small retail locations that at a minimum had 8k of network equipment, with some locations pushing into the 100k+ range based on needs and size. That’s per site. The above is all in USD, but just equipment. Labor can add 30% to the costs.
15k euro for a whole city that includes equipment and installation sounds very fiscally responsible.
I’ve worked in a heavy industry space where the “computers” were just slightly complicated circuit boards working together. No OS, no networking, nothing but circuit logic running hilariously important machines. The cabinets were locked in a small area deep in the facility that was manned 100% of the time, and were rarely accessed, so it would be a big event for anyone to interact with them. There were no windows for “someone with a clipboard” to just be waived in to mess with them.
There was no remote access, and no social engineering possible. Anyone who could work on them was well known by everyone who would be in the room. An insider threat was basically the only kind possible, but the only “hacked” output would just be a failed “off” state, which wouls be replaced.
There really are “unhackable” computerized machines out there, but only because calling them “computerized” is a stretch.