A fair amount of sellers also won’t provide a shipping cost until you commit to buy as they want to make sure that they pass on actual cost to consumer. However, this creates friction as the buyer wants to know what they are paying before they commit.
This has never been a problem for me as a seller. The potential buyer asks me to calculate the shipping cost to his location. This way the price is fair to both parties.
The Audiogon shipping calculator is not even close to reality.
Once we know the actual cost, it can be used as bargaining chip or passed on to the buyer if it’s a reasonable price.
And I never charge the PayPal fee to the buyer.