Note the bolding, above. Nevada taxes all cannabis de facto by weight; Colorado taxes producers by weight unless there is an arm’s-length sale.
Oregon’s 20-percent number reflects a 17-percent state tax and universally adopted 3-percent local taxes. Otherwise local taxes are more of a patchwork, and are ignored. Colorado and Nevada have nominal 15-percent producer taxes. Colorado converts its tax to a weight base for related party or vertically integrated cases. https://newrevenue.org/2017/07/23/is-colorados-new-marijuana-tax-leaky/. Nevada converts to a weight base for all cases. https://newrevenue.org/2017/07/02/nevadas-70-cent-per-gram-tax-on-marijuana-flower/
Details on Washington: Exemption from 6.5% standard sales tax for medical marijuana: https://dor.wa.gov/find-taxes-rates/taxes-due-marijuana. Obligation to pay 37 percent excise tax on medicalamarijuana: https://dor.wa.gov/sites/default/files/legacy/Docs/Pubs/SpecialNotices/2016/sn_16_med_endorsement.pdf.