Explain the following phenomena :

I have observed the following phenomena:

Case 1: Relatively more high-quality Korean ginseng are exported and sold in oversea markets but more low-quality ginseng are sold in Korean local market.

Case 2: Luxuries (e.g. diamonds, jade and pearls) take up larger percentages in international trade than in domestic trade.

Case 3: Larger proportions of wine of better quality (e.g. red win, brandy and whisky) are consumed after the imposition of a per unit sales tax.

Case 4: The average length of airline journey increases after a rise in the per head airport departure tax is imposed by the Government.

Please try to explain why the above phenomena in Economics can be accounted for by the Law of Demand??