I'm curious where your 2% margin came from in this estimate. From what I can tell, that number is often quoted as Amazon's profit margins, but I'm not sure smaller more-specialized online retailers necessarily need to match Amazon's low margins.
If you are manufacturing something then the profit margins can be much higher. However, for retail 2% is fairly solid and likely above average when you include people losing money, but not outstanding.
If you're making $100k to each 50 states, then you've got $50 Million in Revenue and can afford to do it.
If you've sold 10 t-shirts at $20 a piece, then your total sales of $200 isn't worth bothering with.
If we want there to be problems we can certainly create them, but doesn't seem all that complicated if we want it to work.