This is what distributors do. I don't feel cheated when an Amazon sellers offers something that I can buy for 40% less direct from China, or when a store sells me a loaf of bread for $4 that they paid $2.75 for.
If it's worth it to me at the price offered, I'll buy it. If it's not, I won't.
amazon is a bad example for this because they aren't just saying here is x for y$. they force the sellers into paying at least y everywhere, even if amazon has nothing to do with the sale. they are using their semi-monopoly to raise your price on x everywhere. sort of the opposite of the "the market will solve it" approach.