I'd convince them it's an excellent hobby/learning experience. Plus you can always make the financial argument.
3 5850's will use approximately 450-500W continuously while mining and your machine will add a bit more, but let's assume 500 for the sake of argument. That's about 12 Kilowatt Hours/day * 30 days or 360 Kilowatt hours/month. Multiply that by your KWH rate for electricity and you can guesstimate how much it'll cost. So, at 10 cents a KwH you're looking at $36/month in electricity.
Those cards can pretty easily do 330-340 MH/sec, so let's say a flat 1 GH. Using that against the current difficulty with $14 BTC prices (both of which are subject to change), you can expect to mine about 18 BTC or around $250 worth of BTC.
Of course, you now have to deal with a loud/hot box in whatever room you stick it in and all the hassle of getting BTC sold and into your hands as cash but it's definitely worth it.
3 5850's will use approximately 450-500W continuously while mining and your machine will add a bit more, but let's assume 500 for the sake of argument. That's about 12 Kilowatt Hours/day * 30 days or 360 Kilowatt hours/month. Multiply that by your KWH rate for electricity and you can guesstimate how much it'll cost. So, at 10 cents a KwH you're looking at $36/month in electricity.
Those cards can pretty easily do 330-340 MH/sec, so let's say a flat 1 GH. Using that against the current difficulty with $14 BTC prices (both of which are subject to change), you can expect to mine about 18 BTC or around $250 worth of BTC.
Of course, you now have to deal with a loud/hot box in whatever room you stick it in and all the hassle of getting BTC sold and into your hands as cash but it's definitely worth it.
my power cost is $0.28kwh and I got my single 5850 up to 400mhs
I have another one in the mail and I believe you can mine using a pcie 1x slot, so I'll get a third soon