FWIW
in testing i have placed '000's of bets less than 10c
not lays - but "backs"
i am using gruss maybe thats not through the api

Over what period of time Aussie?
I know I only had a few small bets under $5.00 and got the warning email.
Maybe they have changed the rules with the new API.
But I'd have to confirm it with them, as their warning email was quite stern.

over a couple of weeks back in feb 2014
i did cop an excess usage charge of about $6 i think for having over 1000 bets per hour.

They only hit certain punters with the warning emails. At least one of the criteria is being in profit with them. I didn't get hit till I was having to pay premium charges and had stayed off their radar up until that point.