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.