eBay already takes a hefty fee. All of these so-called "regulatory" requirements are handled by eBay's computer systems. After the cost of developing them, there are no incremental costs as the process should be automatic. Look at charging European buyers VAT. eBay has an automated system in place to charge VAT and pay that to the appropriate authorities. It doesn't cost them any more for each transaction, yet they include the VAT as part of the value that they charge their Final Value Fee on.
The latest "cost" for eBay is to report sales to HMRC. Once they have invested in the system to generate the reports and send them electronically to HMRC, there is no additional cost per transaction.
How can eBay justify charging an additional fee to cover the costs of running their business? Isn't that what the standard fees are for?
According to Google, ebay's Net profit margin was 52.2%. So instead of reducing their profit margin slightly to cover the additional development costs, they decide to screw sellers out of their profit.