How Much Money Do Bloggers Make Blogging?:
"Once again these figures hammer home to anyone wanting to get into blogging for money that it is not a foregone conclusion that you’ll make a lot of money from the medium. It is possible to make at least a part time income from blogging and for some to make quite a bit of money from it - but over half are earning less than $3 a day (or $100 a month)."