The cost is actually $9.95 per 24 hour period. Depending on your needs, you wouldn't really have to purchase it every day, but could still use it every day.
Dialup is also an option where the only cost would be for the phone call. Cost is $0.35 for members and $0.75 for other guests for local calls. You would need to have an ISP with a local number - we use Netzero which is a free service with lots of local connection numbers for WDW.
Enjoy!