That should not be the case if Gooding or a third-party agent is shipping it to you outside of California.
Laws are changing... I buy and sell with many auction companies. Unfortunately most of them now have to charge sales tax regardless of where you live. But if you buy as a business and have a tax resale number, you can avoid the sales tax.
That was my experience with RM recently. Gooding, however, as of my last purchase this past October, was not. Could that have changed? Unfortunately, yes. With the way sales tax collection is going, I see why auction companies and higher end booksellers are doing well outside of the USA. For expensive books (which have no import duty), the price of international shipping can be favorable compared to sales tax.
WOW: Yesterday at 1 p.m., I ordered Silver Steeds at Palawan, today (!) at noon it will be delivered to my home in south Germany, including all red tape with customs offices finished! That must be the fastest cross-Channel DHL Express delivery of the last years, especially after Brexit. Well done DHL (and of course: well done by Gavin from Palawan!!!)