Sales Tax

Best of luck sir. Sounds like you’re as prepared as you can be to refute it. 

We know. All good. 
But where you’re at right now is the state got your money and you ain’t getting it back. 
What you gonna do? Go argue the interpretation of RCWs with a $20.31/hr govt employee or their $23.47/hr supervisor?  You’re dealing with menial employees of a state run organization. Only 2 types of people work there  The kind that are too lazy to take a private job that pays more and just don’t want to extend or burden themselves hard enough to think for themselves or analyze anything.  And those who aren’t very ummm smart but are smart enough to know they have job security punching buttons for the govt and it’s really hard to get fired  

Send an email straight to the junk folder of the Georgia AG?  Hahaha he’s the one that ultimately taxed you.

pursuant to my example above (except they didn’t already have my money) imo your only/best bet is try to bend the ear of a supervisor at a dmv and be very polite and apologetic and complimentary (especially if a woman and absolutely, if a “larger” woman….seriously).

Explain that you don’t realize at the time that your purchase was mis-categorized when you registered it.  And that your very sorry for the trouble but that this is a financial strain on you, at a time of loss (you loved great aunt Edna dearly and she loved that RV almost as much).

Dont start out with the legal eze, just that it was taxed as if it was bought from a dealer (simple words, there are 2 types of transactions, well only 1 in WA you get taxed the same dealer or private) and this was a private sale from dear Edna’s estate and there was a mixup.  Only if you’re not getting anywhere or if you are but the person seems uncertain do you bring the 3 letters into it (rcw). 
Remember 9 of 10 people you’d ask walking down the street what RCWs are would A. not know the definition of acronym.  And B. Wouldn’t know what it stood for.  You’d get answers like Really Cool Wigs or something.  
so use that language sparingly and use words like “I looked up the law to make sure I wasn’t mistaken.”  

That’s how I’d approach it  

Good point. I hadn't had my coffee yet.