YSK Free shipping over X amount is not a gift to you because you spend that amount, It is a sweet spot that pushes you to purchase an additional item or something more expensive.
from /r/YouShouldKnow
YSK超過X金額的免運費不是因爲你花了這個金額而給你的禮物，它是一個甜蜜點，促使你購買額外的物品或更昂貴的東西。