Facebook gives you the option of how much to pay and says how many people you may reach with that money. I currently pay $1 per day, which lets me reach about 800 out of my 2000 followers every week. Each post ends up being seen by 50-100 people unless someone interacts with it (such as a like, share, etc), then it can get up around 200-500 depending on the interaction.

I have no idea what a newspaper would charge for similar exposure, but I can tell you that at $1 per day, I'm often paying more money than I'm making from my site.

For comparison, six months ago I was reaching nearly 100% of my followers each week and each post would easily be seen by 500 people no matter what. It's been an absolutely catastrophic drop-off.