The "regular" taxi cab medallion cost averaged $35k in 2017 down from $200k in 2013[1] otherwise you will likely be leasing it and a car from a taxi company. If I recall, the daily buy-in is generally $90-150. So these costs should be included in the calculation.
Fare = $2.60 + $2.70 per mile + ($0.50 per minute while speed<11mph)
[1] https://www.seattle.gov/your-rights-as-a-customer/file-a-com... [2] https://library.municode.com/wa/seattle/codes/municipal_code...