Thanks UB.
I am betting Aus markets only.

According to BF this is the current rule...

This charge(turnover charge) will only apply to customers who during a week meet all three of the below criteria:

have matched back bets on 1000 or more markets which Betfair is subject to a turnover fee from a racing body (‘turnover charge markets’);
have matched back bets with an aggregate value of $2000 or greater on turnover charge markets; and
the total commission generated by the customer on turnover charge markets is less than 1.5% of the aggregate value of matched back bets placed by the customer on those markets.

I am betting on up to 30 races/ markets per day. If I do this 7 days a week then I am betting in 210 markets per week.

It also states that the turnover charge only applies to racing in ACT, WA and NSW.

Unless I have this all wrong, it doesnt appear to me that I could be placing bets into 1000 or more markets in a week using my system.
(of course their web page may not be up to date)

ET