Take the largest amount you have made in a single month then..

Divide that by the amount of hits you got in the same month.

For example, say you made $100 on 5000 hits..

$100 / 5000 = 0.02 per click + 10% = 0.022 per click thats what your rate should be around, IMHO.

Of course, if demand is high, as with anything, the price goes up, if demand is low, the price goes down.

Once you have a solid stats base, you can 're-work' the figures

Regards,

Lee