This is from the SEATAC site:
Taxi
$275.00
On Call Limo
$300.00 - $325.00
Quick Shuttle Campbell River Store in Surrey, YVR Airport, Downtown Vancouver
Sandman Inn - 180 W. Georgia St., Cruise Ship Dock, Ballantyne Pier & hotels
Adult $36.00, R/T $65.00; Senior $33.00, R/T $59.00; Child (5-12) $17.00, R/T $31.00
Greyhound Greyhound Depot in Delta, Richmond, New Westminster, and Vancouver
From downtown Seattle:
Monday-Thursday, $22.23; Friday, Saturday, and Sunday, $24.24
Think I'd for for the Quick Shuttle which departs right outside luggage claim. Hopefully their schedule will work for you:
http://www.quickcoach.com/