I like your optimism Mike, but I wouldn't be planning on early retirement yet!
When I first started betting on the horses [40yrs ago], I worked out that all I had to do to get from struggle st. to easy st. was to back favorites for the place [why hadn't anyone else thought of such a plan? LOL].

AS Xanadu and Thorns have pointed out, TAB SP prices [especially for the place] cannot be known until after the jump, so you can never be certain what price you are accepting.

Theoretically, even if you did manage to get an average price of $1.20p per bet, you'd need a better than 80% SR just to break even and maintaining even that would be impossible, let alone trying to produce a profit.

All said and done, a better proposition for you might be aiming for one winner from 4 bets [25% SR] at an average price of $5w. If you were consistent enough you could make a profit. No easy task but with careful race selection, it's at least not impossible and worth aiming for.

Good luck whichever way you bet.