It depends on how they claim income. If they are a business and they are located in your state then they will charge tax.
I wonder if you can ask for their business tax ID to confirm they are an actual business and aren't pocketing the sales tax.
yes I am in CA and it does not seem to appear that the seller is running a business, they have a personal, not an ebay store acct but who actually knows.......I am just a bit put off by the extra $30 charge for something used. I know you get charged tax on antique or vintage clothes but that's in a retail shop, this is on ebay!!
As an ebay seller, I never charge sales tax on my auctions whether used or new, I paid it already when I bought the item so why should it get double-dipped on, kwim?