Discount stores like Ollie's offer deals beyond comparison in value?

I'm sure you all know Ollie's. The store with the old man's face saying we offer bargains. In the store they offer items at prices that sound like a scam. I just brought a 30$ item for 10$. At wal mart it is actually 30$. But the item seems like the same. There must be a reason why they offer it cheap. Or are they really just a store that can give deals.