First there was the era where anyone could get lots of bitcoins by CPU or GPU mining, but they were worth almost nothing.  Then the era where anyone could mine them through ASICs, and they were worth quite a bit.

Last year there was a massive buildup of mining power, which caused difficulty to go up so far that, unless you have free electricity, it's cheaper to purchase bitcoins than mine them.  Today, big mining operations are shutting down because their electricity costs exceed their income.

My BFL miner cost $1,400 and does 60 GH/s.  It was bringing in about $20 per day when I first got it, but it's down to about $0.20 per day now due to the difficulty increases.  Today it's essentially just a space heater.  I have an oversized solar array on my roof, so it's cheaper to heat the house with electricity than natural gas.

If you have free electricity, you can pick up great mining hardware very cheap these days, but unless the difficulty drops or the price increases substantially, you're not going to make much.