eBay

That is legal for eBay to collect sales tax based on the buyer's state residence. The buyer is responsible for the sales tax so it does not affect the seller. The tax % varies by state. This new rule has been applied for a few years. 

no I guess what I’m trying to say is if I sell something for $300 they could charge me the 13.25% but if the taxes $30 they are also charging 13.25% on that $30 so they are collecting the 13.25% on $330 not the sales price of $300

They also take a % of whatever you charge for shipping.