or a large number of Amazon EC2 instances, you need to cover the costs. This is a regular business for dumpers, not the investment vehicle.
With a c3.8xlarge Amazon EC2 the Monero price should be more then 25$ for 1 XMR in order to cover the costs:
1.68$ per hour * 24 hours = 40.32$ per day
<MoneroBot> With 1000 H/s you should get 1.36 XMR per Day
40.32 1.36 = 29.65 $ per 1 XMR to just cover the costs.
The people currently selling are mining on already payed GPU rigs with free or cheep electricity, system admins or students with access to large CPU farms (electricity payed from their institution), botnets (you should be very ignorant if you can't find if a botnet is using your PC to mine) or bought earlier on lower prices. They'll continue to sell no meter the price, because it's free money for them. I doubt they are selling all the mined XMR, but they are selling most of it. Home mining on a i7 CPU is still profitable, but you are mining 0.2 XMR per day. By the way 10% of all the XMR are now mined - 90% to go - still high inflation, but it's becoming irreversibly lower each day and with the XMR potential the price won't go much lower. I doubt the price will touch 0.003 again and I'll be very surprised if it touches 0.002. If it goes below 0.0018 (even if all the governments put a ban on XMR before the I2P C implementation is ready) I would never buy any alt again.