The cost of Showtime varies depending on your TV provider. For example, on DirecTV, a channel costs $13.99 per month.
On the other hand, Spectrum users can get it as part of their package without any additional cost (except for their Spectrum plan).
On Amazon Prime Video, Showtime is an add-on channel that will cost $10.99 per month. However, it also comes with a 7-day free trial during your first purchase.