Without knowing the composition of the winning prices, it's impossible to to say what the minimum acceptable price could be.

The theoretical at 33% S/ is just a shade over $3.00.

You see the average could be made up of evenly distributed prices between say $1.80 and all the way to say $15.00. in which case
your lowest acceptable is of course $1.80.

But if your prices are mostly hovering around the $2.50 mark and you had a couple of large dividends of say $30.00 then your average price could still be $4.50 but unless you can repeat those
big divies at regular intervals, you are doomed.

Average is important but the median price probably tells you more about the prices you get.

I think the dogs you select probably would give a $4.00 average price without relying on large dividends, in which case I'd say $2.00 minimum is OK but you have to monitor it for a while to see that is not relying too much on the larger payouts.

In other words you should get a good distribution of $2-3-4-5 and maybe a be a few larger divies.

This goes for your second third fourth and so on selections, you can work out your strike rate and the average divie required, as long as they are profitable I can't see why not betting on them.

For me personally my second selection in horse racing is the one I mostly rely on for profits.

Good luck with it.