Proposing a Profitable and Useful Horserace Betting Gizmo

[mindflayer]

Correct me if I am wrong. (I have only been to the track a few times)
Does not the fact that this calculator exist (in large numbers) and the fact that the House adjusts the odds based on the bets placed make the calculator -EV.


The scenario goes something like this.
YOU have the lone calculator.
Calculator shows odds of favourite to win paying 4:1
Calculator shows his calculated odds of winning 3:1
You make a decent bet on the favourite.
The house does not adjust the odds due to
the small wager you placed.
You win this bet 1 in 3.
It works well and you make money.

You sell a few million calculators.
Everyone at the track has a calculator.
It showes the favourite to win pays same 4:1
It shows his calculated odds of winning are 3:1
The everyone with a calculator makes this bet.
Due to the large number of bets placed on this
horse the House adjusts the odds down to 2.8:1
Favourite wins this race 1 in 3.
Everyone loses.

Is this not like changing horse racing into roulette?!?
Perfect odds could be calculated for each Number (horse) winning and the house would have only a small 3% vig on each bet. Where people bet Outside the odds, the house has a greater advantage because they simply adjust the payout odds down.