Important Note: 30 single packs in a shop is not equal to a sealed box of packs!
To my disappointment, I opened all the packs to discover 0 Super Rare/Ultra Rare/Ghost Rare cards. I got all rare cards and none of them seems useful. The only scant consolation was that I got 3 Solemn Warnings but those are common cards in the box (OCG). On opening the packs did I realize about half of it has a safety warning sticker on them, which means the packs do not come from the same box.
I should have inspected all the packs before buying. I think this experience may not be new and others might have already encountered it. The shop people could have allowed the customers to feel/weight for packs or they might be the ones who sieve out the "good" packs? The shop happen to have a weighing machine at the counter too. This is a very expensive lesson for me. Buyer Beware!