Even simpler: do away with all transaction fees. Theses should be covered by the buyer fee anyway (as per how they defined the buyer fee).
Paypal strongly suggest not to apply a surcharge for their payment, unless merchant has very tight margins. Envato does not have tight margins, really far from it.
Paypal’s guidelines are most likely aimed at small businesses who may lack the resources to prevent such ill-advised idea. A major company such as Envato should know better obviously. Their going forward with this reveals a very dysfunctional top management.
By the way, Paypal adds that this surcharge you should only apply if you really have to, can only be expressed as a percentage of the transaction, never as a fixed amount. By doing so, Envato is in direct breach of Paypal’s terms.