Cheapest transportation?

Travel Info
what is the cheapest way from airport to the pier in seattle

Travel Tips

King County Metro bus -- you can take it from the airport to downtown for probably $2.50, then you can ride around downtown for free (to whatever pier you are looking for).

I'd suggest using their website Trip Planner, here's the link:
http://transit.metrokc.gov/

Other options would be Shuttle Express (probably $25-ish) or a taxi ($35-40).

Others
having a friend pick you up for free
my opinion is a bmx bike but thats just My opinion
Sound transit (communtiy bus transport)....
If you are arriving at the Airport with Luggage and heading for a Cruise Liner - you should not be talking about "Cheapest Transportation".
If the Cruise ship doesn't provide Transportation - take a Taxi.