I've seen the graphs. But I have yet to see an explanation of how you actually make money that way.

The best I've heard are theories along the line of a DOS attack. I.e.:

1) Eve sends an order, receives an ack, and receives the quote. (The last two steps can be in any order.)

2) Alice receives the quote, and spends more time processing it than Eve spends on the order, ack and quote.

3) ???

4) Eve profits. (Perhaps because Alice and Eve are both HFT's, and this attack lowers Eve's latency relative to Alice?)