Probably amazon buys it from the same supplier, but they can sell it for less margin, because they don't have the overhead of running a store, and they have the scale of being amazon.

> sells it cheaper than they can buy from the suppliers

Perhaps they miswrote, but the comment says that Amazon is cheaper than the supplier.

It's somewhat common for a large manufacturer to accidentally undercut themselves. For example, one branch selling to Walmart and another selling direct to restaurants. Sometimes the price at Walmart, even after Walmart's margin, is cheaper than the direct price. The restaurant-sales group is horrified as they lose customers to Walmart and goes running down the hall to tell the bigbox-sales group to raise prices.