The price is the same as for 1Gbps and 10Gbps (~60USD/month) - though the initial setup price differs: ~300USD for 25Gb/s vs <100USD for 1Gbps
The actual speed within network is indeed 25Gb/s to some fellow users running speedtest.net servers. Inside Switzerland it's maybe ~15Gb/s to some well connected servers in the area of Zurich, and ~10Gb/s across EU. Tested with speedtest.net and iperf.
A bunch of other Speedtest.net servers were located in Amsterdam and took a very similar route via Cogent but none of the others broke the 10Gbps barrier.
It is for sure often Init7 though. Those peering relationships it built up have become a bit of a weakness because they're usually limited to a 10Gbps port.
Aside from that I have a Mikrotik CRS305-1G-4S+IN to distribute 10Gbps to a few other devices.
I'd love for everything to be 25Gbps but the hardware is just too expensive.