Quite an interesting proposition the answer to which revolves around the Lay price you can obtain.

Take the scenario presented. That generates a Win SR of +/- 20% (or 80% LSR if you prefer) using a sample of 30,400. Hence on the 'back' end you need a net $5+ to break even. In a theoretical Lay run of 1,000 races you're going to run into 7 runs of 4 outs to play havoc with yr bank.

Based on that, you can do the math on your fingers and determine the minimum net Lay price that needs to be delivered to make the profit you're looking for.