Yes you can save money. How much depends on how much you brew.
I knew I'd save money, but that wasn't the major reason for buying a mill. I wanted control over the process; I'm not dependent upon any LHBS doing it right, or having to worry about their crush. I'm able to get exactly what I want.
I get my malt from Ritebrew; either I pick it up or I have someone else do it if I'm lucky. They have 2-row malt for $38/50 pounds and Maris Otter (a fave) for $53/55 pounds. That's 76 cents a pound and 98 cents a pound.
At my LHBS, I pay $1.50/pound for 2-row, and I can't get Maris Otter at all (though I suspect it would be $1.75 or more).
So I'm saving 74 cents per pound. A typical brew has 10-12 pounds of grain, so just for the sake of argument, I'm saving $7.50 or more per brew.
From that, you can do the math. If you buy, say, a Cereal Killer, you've paid for it after maybe 14 brews, and at that point, it's all "profit," or, if you will, savings. AND, you control your crush.