In your scenario, He buys a car worth 8,000 USD from Japan and pay 8,000 USD to SL Gov as Tax , then send the remaining amount which is 16,000 USD to his parents in cash as usual >>> SL now has 8,000 +16,000 = 24,000 USD net
Same Effect........... But
But with time he and his parents will realize that they profit more from buying cars and selling with a margin in SL than just sending money. So, he will send more and more cars here instead of USD.
So for his personal gain, he will now buy 2 cars worth 8,000 USD each by paying 16,000 USD . Then he will send it here in SL by paying a Tax of 16,000 USD. (By now he has utilized all his USD, which he usually sends as cash to SL.) He sells the car with 15% profit in SL. >>>> SL now has 16,000 USD net within the country (got as TAX revenue)
24,000 USD vs 16,000 USD