[1] http://www.aopa.org/Advocacy/Regulatory-,-a-,-Certification-...
It still cost me $15k (in 2012 -- airplane $11k, instructor $4k) to get my Private Pilot License -- plus another $2k in optional expenses like a good home simulator set-up, iPad software, books etc. -- some of which arguably should have made my training more efficient.
While I don't know the costs of getting a Sport Pilot license, I have wondered if it would have been the better route for me.
The difference between the times I fly with a VFR Private Pilot license is virtually no different than I would with a Sport Pilot license. I rarely have more than one passenger (one is limit for Sport Pilot license), and I rarely fly at night ('engine out' at night is beyond the risk I'm willing to take), I've never been above 10k feet.
You'll need to study and pass a written examine so you'll have to either purchase self-study books or take a ground school class. (This is relatively cheap, a few hundred dollars.)
You need to log 40 hours of flight training time. Depending on locale, anticipate paying $100-$150 per hour for a flight instructor and $100-$150 per hour for plane rental and fuel. So that's $200-$300 an hour times 40 hours so a ballpark estimation is $8000 to $12000 MINIMUM. Depending how quickly you get to flying solo (with your instructor on the ground) and how well you do will determine if your flight instructor will sign off after the minimum 40 hours.
EDIT: You'll need to pay for the examine and I forgot, you'll need to get an "FAA physical" and an okay from a physician which you'll also have to pay for (unless you can get your health insurance to pay for it as a yearly physical examine).