This is a really good question. Too few people pay attention to costs.
I target paying 6% of my returns in costs. To be precise I conservatively target around 1.5% of account value a year, which may be a larger or smaller figure depending on how returns come out. That's made up of 0.3% in commissions (data costs etc are tiny) plus 1.2% in slippage.
Actually last time I checked I only paid 0.65% of my account value in costs. And my average return is running well above backtested expectations, at around 50% annualised (this won't last, but still this is the figure you wanted), so I'm only paying 1.3% of my returns in costs, so much less than 1% just in commissions.
I notice you didn't include slippage. It's worth including that since it will normally form a bigger part of your costs than you realise.
20% of returns going just in commissions seems extremely high to me.... but I would imagine you're trading a lot quicker than I am.
GAT
I knew you care about cost.
I've seen your awesome journal.
Can't be more professional than you.
Unfortunately I can't hold overnight,
I can't meet the needed requirements ..
Thus I'd trade more and shorter than you.
But I'm not that proud seeing your ratio =P
However I've got no slippage cost. Really.
I trade mainly with limit orders but anyway.
The ES would have no problem absorbing 1 lot.
I have been really surprised about your slippage.
That's because I am still playing in a kindergarten.
Well done GAT, that's an efficient machine you have.
More cost are taken into your equations,
But you still manage to beat me.
Hands down,
& Thanks for sharing your experience.