There is no way I would pay $120, or even $100 for an oil change, I don't care if they top off all fluids including...nevermind.
I say that because I have everything I need to do it in my driveway - jack, oil pans, etc. Like someone else here said as well, it's always nice to get some one-on-one TLC time with your car.
As far as savings goes, my car takes a little more than 6 quarts of Mobil 1, which can be had at Walmart in 5 quart jugs for $22 a jug. That works out to about $30 for the whole change including the filter. Add a couple bucks if you want for the random fluids that I have in the garage for top-offs.
So saving $70 bucks ... that a free tank of gas!