if a person pays a sex worker $100 and the sex worker (assuming no middlemen) reports it as just someone friendly giving them money for nothing in return (gift) then that transaction itself won't be counted in GDP.
if a person pays sex worker $100 and the sex worker runs a nail salon as a front, then that $100 would be counted because the 'customer' paid to get their 'nails done'.
i think it would depend on how its laundered.
if a person pays a sex worker $100 and the sex worker (assuming no middlemen) reports it as just someone friendly giving them money for nothing in return (gift) then that transaction itself won't be counted in GDP.
if a person pays sex worker $100 and the sex worker runs a nail salon as a front, then that $100 would be counted because the 'customer' paid to get their 'nails done'.