I found this at :
Washington State Legislature
How it used to be:
An alternative fuel vehicle retail sales and use tax exemption was in place between January 2009 and the end of May 2018. It was modified in law several times. The most recent version in place, enacted in 2016, was a retail sales and use tax exemption for new passenger cars, light duty trucks, and medium duty passenger vehicles that: (1) had a
base model Manufacturer's Suggested Retail Price (MSRP) of $42,500 or less; and (2) were either exclusively powered by a clean alternative fuel, or used at least one method of propulsion that was capable of being reenergized by an external source of electricity and were capable of traveling at least 30 miles using only battery power. Both purchased and leased vehicles were eligible. Tax exemption eligibility was capped at $32,000 per eligible vehicle.
How it is now:
The alternative fuel vehicle retail sales and use tax exemption is reinstated using the same vehicle qualification criteria in place between July 1, 2016, and May 31, 2018, except that the qualification requirement related to price for new vehicles is changed to only permit vehicles with a
sales price (including any trade-in value) or fair market value of $45,000 or less.
For new vehicles purchased or leased between August 1, 2019, and July 31, 2021, the maximum amount eligible for the tax exemption is $25,000; for vehicles purchased or leased between August 1, 2021, and July 31, 2023, the maximum amount eligible for the tax exemption is $20,000; and for vehicles purchased or leased between August 1, 2023, and July 31, 2025, the maximum amount eligible for the tax exemption is $15,000. For used vehicles, the maximum amount eligible for the tax exemption is $16,000 from August 1, 2019, to July 31, 2025. The seller must keep records necessary for the DOR to verify eligibility, and a person claiming the exemption must also submit certain specified information to the DOR.
So it doesn't matter what the base model price is now, only the actual sale price on your invoice.