Again, the situation is exactly the same whether the means of transaction was PayPal, Bitcoin, a credit card, or an envelope with some paper bills. Some actual humans need to be involved in a merchandise return situation, which costs a business money to deal with.
Regardless, transaction costs increase due to mediation. Paypal is compelled by regulations to verify the parties involved when facilitating a transaction; this increases the cost. People need to work so that your transaction finalizes. How is this "exactly the same"?
Digital currencies are digital tokens that maintain their value by virtue of one's possession of it, as opposed to one's identity like as in a bank or credit card or PayPal etc.
So, your digital currency operates similarly to PayPal but without the need for identification, correct? What happens when authorities demand client identification from you? Sooner or later, you may be classified as a money transmitting business.