Cab rides into downtown Seattle from Sea-Tac International Airport run $42-50 one-way, and are available through Yellow Cab. Once in downtown, you can take your pick.. . The best way to find one is to have the hotel or restaurant call one for you if they don’t have some waiting around. During peak hours on weekends, you may be waiting 10-15 minutes before having success getting one to stop, let alone drive by. Also be advised that while cabs are metered from the airport to downtown, cabs charge a flat fee from the downtown hotel zone to the Sea Tac Airport. Currently that has been set at $40. Seatac Airport has an agreement with one taxi firm who's cabs are stationed in the Seatac garage. That firm is currently Yellow Cab. STILA is the on site limo and towncar provider at Seatac established by the Port of Seattle. Since these are flat rates, the amount for a limo into Seattle is often as cheap as a cab. Towncars and limos from the airport are available by calling #55 from the phone near the hotel ads in baggage claim. a The current rates are $45 for a towncar and $25 for a for hire vehicles.
There is a pretty nice fare estimating tool available so you have the ability to compare. The site lets you plug in a destination and comes up with a fare but it doesn't include any airport fees. In general the for hire vehicles almost always are cheaper then a cab and the advantages multiply if you arrive in rush hr or during traffic as wait time in cabs are $.50 a minute, where for hire vehicles are always a flat rate.
Here is the ''official' airpot taxi site with fare estimator. It shows an avg fare into Seattle at $52.50 making the flat rate limos a great value.