Two bets,

I disagree as you will find those horses which are undervalued will make up a bulk of the strike rate for a system. For example lets take a hypothetical 10 bets.

Bet 1 $2 WIN
Bet 2 $5 LOSS
Bet 3 $5 LOSS
Bet 4 $5 LOSS
Bet 5 $5 LOSS
Bet 6 $2 WIN
Bet 7 $2 WIN
Bet 8 $5 LOSS
Bet 9 $5 LOSS
Bet 10 $5 LOSS

This system selections have a 30% strike rate ... So anything above $3.30 shouold produce a profit ... but the thing is only those bets under $3 are actual winners.

I know this is hypothetical so I ran an actual ratings (unitab rating) to see what happens ie Top 100 raters on unitab)

Without any filters:
35360 Selections
Strike Rate : 23%
WIN ROT = 86%

So assuming this anything over say $4.50 should be a long term winning system :

15393 Selections
Strike Rate : 12%
WIN ROT = 83%

The system has got worse .... So lets say we really need value and should be taking double the chance so $9 +

4442 Selections
Strike Rate : 7%
WIN ROT = 85%

I think this demonstrates my point .... As the odds increase the probability of a seleciton winning decreases. Therefore if you do not know the "true" chance of a horse you are not getting value.

Good Luck.