What is the $100 to $275 for, the fridge or chest freezer, or the conversion stuff?
I did all mine seperate. Faucets & Shanks were about $30-40 each. Hose isn't to expensive (I use red for CO2 and blue for beer). I have a 4 way splitter for 4 kegs, that was about $30 IIRC. ball lock fittings are about $5 ea and you need 2/keg (one in/one out), I have a refrigerator thermostat to keep the chest freezer temp around 40º that was around $50 (though I don't think this would be included in a kit). The biggest expenses are going to be corney kegs and the CO2 tank. I was able to get myself a 20lb CO2 tank for free. I just exchange it at a local fire extenguisher place for like $15. Though a 20lb tank can last me a few years. You might be able to rent them as an exchange at a fire extenguisher place. I forget how much my regluator was. Corney kegs can range from $20-80 depending on where you get them. New ones are very expensive. Used ones are usually perfectly fine.
The big difference in kit prices are probably going to be the size of the CO2 tank (5lb, 10lb, 20lb) and if it includes a corney keg.