Well, perhaps you might save some $$$ in the very long run. I'll be honest, I'm paying $110.00 for a 15.5 gal keg of Shiner... that is about $.65 per 12oz glass. Not bad really, and much cheaper than the $7.00 per six pack I find at the store.
The fridge? Free is good if you can find one (try Craigslist). I gave $80 for mine... delivered, and it is a very nice 20 cu ft model with top freezer, so there are good deals to be had if you are patient.
As for the kits on e-bay... I purcased mine from the Beverage Factory (probably the same ones you are looking at). I can tell you that their kits are of good quality. All the components are commercial grade and the installation is straightforward. I purchased the deluxe kit with CO2 bottle and drip tray... all you need is a fridge, 7/8" hole saw and keg of suds. This kit is currently going for $175.
So, as you can see, there is some initial cost... $200 and up, depending on the kit and fridge options, so it will be a little while before you realize any savings. What you do get is some MAJOR COOL FACTOR... especially when you have friends over for a BBQ. Most people have been blown away that I have fresh, ice cold beer and frosty mugs in my garage... it is fun. Not to mention that there is nothing better after mowing the grass in late June.
Here is the biggest selling point with the wife. All those spices, rubs, jugs of cider, meats and such that keep crowding the fridge in the kitchen... all that stuff can be kept in the kegerator. I actually have two deep freezers and two refrigerators, but I keep all my specialty stuff in the kegerator. Even though the wife loves BBQ, she does like that added benefit of the kegerator.