Free: Contests & Raffles.
Currently because of COVID we cannot hold any Trapper Education classes. There is an online class you can take https://wdfw.wa.gov/hunting/requirements/education/trappingThe class itself is free. The tags are not issued by the State. You purchase them privately, name /address or Wild ID#. A quick search found a supplier selling them $13.00 for 50. Prices may vary. Be aware WA is a cage trap State so how much of your stuff you can use from another State is a question mark. You'll see when you look at the manual available in the link I posted.
Look under small game license.Good luck