Here's another list of bus transfer options:
I thought the cruise companies provided transportation from the port to Anchorage. Someone told me once that the cruise company's bus was free or they could upgrade to the Alaska Railroad for an extra $59 or so (this was a few years ago, though). You might want to check with your cruise company to see what transportation options they offer.
And a little plug for Alaska itself: do us justice next time and spend some time in the state itself. It's so much grander and more majestic than what you see from a boat...(and if you can change your flight reservations to allow a few days or even a few weeks after docking, you won't regret it).