The first year gives you a special discount, then the price goes up. Please see:
Eligible students 13 and older and teachers can purchase an annual membership to Adobe® Creative Cloud™ for a reduced price of $19.99/month for the first year. After the first year we will renew your contract automatically for another year at the then-current standard monthly price (currently at $29.99/month), unless you cancel. This pricing is valid for purchases of an annual plan, which requires a 12-month contract. This pricing is available for first time membership only and limited to eligible education customers who purchase directly from the Adobe Store or by calling Adobe Sales.
Once you are no longer a student, your subscription will renew at the standard price (which is currently $49.99/month).