What the frack are you paying for your electrical rates? Either way.
1 x Power for PC 1 year days -300$
3 x D3 Accounts - 160$
1 x 3DB lifetime - 75$
If you can not over the period of 3 months make back your 500$ investment. You do need to go find a real 9-5 Job scrubbing toilets at McDonalds.
You are so ridiculous, let's have a go at real electricity component shall we?
321 Watt <-- this is the number an i7 (very efficient ) with a gtx 560 will consume per hour, just playing crysis. The biggest amount of voltage will be drain by the CPU, so let's hope here, that crysis is CPU intense or I would be even worse off.
In germany 1 kilowatt hour costs 0,22 ?. those 321 Watt are 0,321 kWatt so we do:
0,321*0,22*24*30,4375 for an average month = 51,58 ? Without monitor, which you might want. So yes, very very cheap and while you have your imaginary 300$, i have the very real 600? per year.
So now let's go further with your assumption of 1$=1 million and just say 1? = 1 million to keep currencies consistent.
A sale of 1 million would generate me as shown earlier after blizzard and paypal 0,51 ? ( to be fair sales of 2 million/3/4 would be more profitable due to paypal eating a large chunk as it is even more in europe btw )
4 accounts on that PC, let's assume 300k per hour per account therefor generate 1.2 million gold per hour.
1,2/hour * 24 * 30 = 864 millions per month not counting maintenance, malfunctions to compensate for the earlier unfairness of assuming we always sell in stacks of 1 mil.
I also assume a so heavily botted account will vanish after a month and add another purchase(not counting the rebuy of goldgear)
Assuming 45? per copy: that's 180 ? additional cost, we also don't deduct the releveling time here so now let's put it all into a number:
864million gold will be 864*0,51? on our paypal: 440?
-180? for repurchase: 260
-51? electricity ( btw this is more then 10% of what we would actually earn, so much to "little"): 209?.
If you now start to deduct goldcost for new gear and days of releveling, maintenance and stuff that number will shrink(while for maintenance your electricity would also drop to 1/3 during that duration if we assume complete idling.
So actually calculating in favor of profits, it would be time to say doomsday when we hit 1:1 ratio. Especially when they start to catch faster then 1/month.
Edit for eddie: Of course that calculation holds nothing for now. It is worth way more. I just wanted to point out, that it won't automatically stay profitable just because it is automatically generated.