All of the Celebrity Solstice-class ships have in-room wifi.
As for cost, you can do it ala carte at 65 cents a minute or with a package where the rates reduce the larger the package. For example, a 90 minute package reduces the cost to 55 cents a minute. By the time you get to the largest package the price really reduces.
You are not purchasing time for a particular computer. You can use your package simply by entering the user name and password you associate with your onboard account when you log onto the ship's network and open your browser. So you can use the time on your laptop, your significant other's laptop and even the ship's computers.