it's not that either. it's the total value of all transactions.
if you paint a masterpiece worth millions and keep it in your closet it has negligible impact on GDP. only once it is sold does it have an effect.
if you paint a masterpiece worth millions and keep it in your closet it has negligible impact on GDP. only once it is sold does it have an effect.
Services to facilitate selling [auction fees, commissions, shipping, etc.] are new services and so get counted, but the underlying asset's resale is not.