The OP was inquiring about CDN access which certainly isn't necessary for those needing to keep in touch back home.
Internet plans typically are billed by minutes, i.e. time spent logged on to the gateway which allows surfing. Some plans are by data buckets. Some can be unlimited. Speed varies of course. The fastest systems provide close to 600mbps throughput to the entire ship and at times of low utilization it's quite fast. Inmarsat-B systems during peak times will seem like the days of using spaghetti proxy on a K56 flex modem in an office of a dozen users while two were forwarding AVIs of the dancing baby through their AOL accounts!