Now we have some math! Thanks for explanation guys, I think I'll skip.

I we're talking about math, we need proof
These guy's proved a returned investment in 2 weeks: http://arstechnica.com/gadgets/2013/06/how-a-total-n00b-mined-700-in-bitcoins/
Anyone disagrees?

Based on experience?

Hi all,
To be honest I'm completely new in the bitcoin scene, but after reading the ArsTehnica article the geek in me became interested in mining. Not so interested to spend a lot of (real world) cash on hardware, but enough to spend some. I was thinking of starting with the Block Erupter USB, any suggestions for a noob would be appreciated. Anyone has an idea of the real world price and availability?

Thanks.