回复：这些钱我该不该给?

By law, you completed a legal purchase. They told you a price, you paid, they gave you the goods. Whether it was $100 less or not, it's not your concern.

On the other hand, if it was a small store, then I would give the money back, since it's hard for them to make the money. The profit margin in computers is very small. Sometimes, even in big store, each sales person is responsible for his sales, so the $100 will come out of his pay.

If it was me, I'd give the money back, especially they called...