According to the tweet, if a $1.00 app is refunded the customer gets back $1.00 from the developer and Apple keeps $0.30. So each refund costs the dev more tha

According to the tweet, if a $1.00 app is refunded the customer gets back $1.00 from the developer and Apple keeps $0.30. So each refund costs the dev more than they took in for the sale whilst Apple always pockets the 30%. How can a refund cost the dev $1.00 if they only took $0.70 for the sale?