Paypal's money market yeild is currently .06% per week. At that rate, with $1000, you make .6 dollars a week, and buy maybe a bitcoin each month and a half...the discussion here is about earning a bitcoin a day mining, so I'm assuming you're down under a third of the mining return.

Assuming the cost of the electricitiy is 1.26 cents per kwh, and your machine is running at around 800 wats, constantly, that's 720 hours and 576 kwh, seven dollars a month...so the cost of running doesn't seem to be that high either.

Edited for bad math. May continue to do so. Please point out errors.