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.

Right! What a rip off! 

They charge 13.25% of whatever the complete total you pay for an item. I have sold on eBay since the beginning and have sold many thousands of items. Combining the approximate shipping cost to the furthest city away from me, factoring in box & packing helps me determine a Buy it Now price. Then I add 7% to the final cost to the buyer as I always offer free shipping. This way sharing the the eBay fees with the buyer and only pay about 7%. Selling on eBay might seem expensive, however the results, due to massive exposure, lead to quick, easy turnarounds. Then there are the easy shipping labels, checkouts, buyer & seller protection. I am now nearing the end of liquidating my record collection of over 700 album, only about 200 to go. To me it is not a rip off at all and an easy way to buy & sell online.