Depends on which way you want to go. I personally do extract kits, which are a bit more expensive but less complicated. If you go all grain, you may be able to get ingredients cheaper, but you need more gear to brew.
In order to do extract kits, you need the brewing gear (roughly $70), a large pot to boil water in (I paid $20 for a crappy one at Walmart, they can run up to $100 easily), the actual kit (around $30 on the site I buy from), non-screw-top bottles (free if you save them), and caps ($1.50). Add in shipping if you buy online and it can run you about $175 to get started.
This will get you your first 5 gallons of beer, which is about 48 12oz bottles. Obviously the gear and pot are a one time cost (if you take care of things) so your re-occuring costs will be the kits, caps, and sanitizer when you run out (pretty cheap and you get a large quantity).
Some folks will talk about your time brewing needing to be factored in to the cost. I've seen forum posts on another site where people say their free time is worth $25 an hour, so they add $100 to their brew cost. My take on that is it's called FREE time for a reason, so I don't factor that in, but up to you.
So at $8 a six pack, you would spend about $64 to buy the same amount of beer. There (theoretically) is a break even point, maybe 4 or 5 kits, but you can figure that out. You'd have to see if there is a local home brew store that you can get things at or if online is cheaper.
There are a few tips to reducing costs that I can give you if you decide to purchase online.
First, pick a readily-available brew kit and price it at multiple sites. I chose an Irish Red and went to maybe six sites and saw what it would cost for a kit to show up at my house. Some sites include more in their kits than others, so while the base price may be cheaper at one site, after buying the other necessities, the actual price may be more than another.
Second, check the shipping policies. The kits are around 10-12 pounds each, so it's not cheap. I found that if I bought two kits at one time from a particular site, the shipping was only a dollar or two more on the second kit. So I plan out my next 2-4 brews in advance and buy all at once.
Finally, don't do this if you want to save money. While it is possible if you take care of your equipment, if you get bit by the brew bug, it can get as expensive as you let it. I started with a basic kit (that I got for basically nothing) and ended up buying two more fermenters and two carboys so I can have 25 gallons going at once. It sounds like a lot, but 10 gallons of that is apple wine that needs at least 6 months to ferment and another is something that I brewed in January 2013 for Christmas gifts this year. I'm pretty close to cost neutral, but if you factor in water, electricity, etc I'm sure I'm down a little bit. I try not to think about those costs because I don't feel like figuring them out!
I will say that I'm really glad I got into this hobby. It is pretty satisfying when you bring your own beer to a gathering and people ask what brand it is and where they can buy it. There is so much to brewing that it can be as basic or complex as you personally want it to be. You don't have to spend hours and hours studying and learning everything there is to know about beer in order to brew something tasty. I'll fully admit that if the kits I buy didn't have instruction sheets, I'd be lost. But my beer is good and right now that's about all I want out of it, so until I want to further my knowledge, I'm content existing at the level I'm at.
So that was a pretty long answer to your question. I hope it was helpful, but if it wasn't or it spawned more questions, let me know. I'll shut up now!