I recently took an interest in mining but the standard Bitcoin profit calculators told me the sad news: that my PC would produce such a pitiful number of coins (like $20 worth a year, even with some simple gear) that it wasn't worth it (especially when considering electricity costs).
But I happened upon a litecoin calculator and put in the same values (20 GHs/s, current difficulty, my computer's wattage, power costs, etc.) and the calc told me I could mine around $500k worth of LiteCoin (after exchanging to BTC then to USD at the current rates).

I'm assuming something's very off. Here's the calculator: http://www.coinwarz.com/calculators/litecoin-mining-calculator

I'd be getting two Butterfly Labs 10 GH/s USB blocks ($50 each) and run my AMD Radeon 7700 GPU for a little more. I have a 250 watt PC and power's about 0.12 a kW.
What's broken here, or can I really get rich on this alt currency?