Hard to give an exact number, since BTC fluctuates like crazy and the amount mined depends on the rig, but:
Cost of rigs is in the thousands (some of these guys are spending upwards of 20 grand on these things), plus the excess cost of electricity to run them (hundreds a month). Meanwhile, those things will mine a fraction of a coin per day to start with (between $5--$15 at current prices, I'd estimate) However, as time goes on, it gets harder to mine blocks, meaning that you need to invest in more equipment to prevent your income from drastically declining.
Basically, the only way to break even (much less make a profit) is for prices to magically skyrocket up to thousands per coin (never going to happen, no one will adopt such an unstable currency) or try to get away with mining at work (which will get you fired).
(Oh, and if those rigs fuck up and die, you can lose all of your mined coin.)