Ordering Black tea from iHerb. It is the same tea. How come ordering from overseas could be a lot cheaper?

Black tea is quite expensive in Seoul.

Ordering from iHerb is a lot cheaper way to buy black tea in Seoul.

Harney & Sons, Earl grey Supreme tea, 4 oz

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$7.50

1

$7.50

Twinings, Origins, Ceylon Orange Pekoe Loose Tea, 3.53 oz (100 g)

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$5.41

1

$5.41

Twinings, Classics, 레이디 그레이 루즈티(Lady Grey Loose Tea), 3.53 oz (100 g)

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$5.41

1

$5.41

Just a Leaf Organic Tea, Noble Keemun Black Tea, 3.5 oz (99 g)

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$7.95

1

$7.95

$10 discount at first buy in iherb with this code "DAG160"   http://www.iherb.com?rcode=DAG160