Forget the comission stuff to Betfair - let me elaborate to see if I can get you to get it proplerly Sportz.

Back to the example - you put $100 on the horse at $3.50, collect $3.50. If you want to LAY the horse, but the maximum you wish to risk is still only $100, then you lay it at $3.50 and allow the punter to have only $40 on it with you, because them having $40 on it with you means if it wins you lose $100 (3.50 * 40 = 140 - $40 stake). So by laying it if it loses you would win $40, and risk $100 to do so, whereas if you risked your $100 on it to win you'd profit $250 should it do so. The difference is - of course - that a horse at odds of $3.50 will lose more times than it will win.

Does that help? Keep asking, Sportz, we'll crack it yet.

Duritz.