It depends on what you're planning to freeze. I think it absolutely makes sense if you are preserving stuff you've grown, or bought cheaply in season. It doesn't really make sense to me to have a freezer to keep a litany of ends and pieces and processed, packaged stuff.
We had a 7 cubic foot chest freezer for several years, and I liked the size, but organization was always a problem, and food would sort of fall to the bottom and be hard to retrieve, and didn't get used very systematically. Last year we upgraded to an upright freezer, and it has been much better in terms of regularly using the food that's in there, and being able to keep it properly stored, and rotated through. Power is fairly cheap here, and I think the chest freezer cost about $2/month to run, and the upright, which is about 15 CF, is probably $5-6/month to run. It currently contains a locally raised, county-fair-blue-ribbon-winning beef quarter, half a lamb raised next door to my stable, two wild-caught salmon purchased in season for $5.99/lb, peaches and blueberries purchased cheaply in-season, many jars of different pestos from my garden produce, ham bought cheaply at Easter and portioned out, fancy center cut bacon bought at 60% off of regular price, 17 containers of Hatch green chile I just processed during their brief season, several free-range chickens purchased on sale, and homegrown green beans and okra. Last fall it provided enough space that I was able to take advantage of buying fresh turkeys the day after Thanksgiving for 39 cents a pound, and then later stash their carcasses and random leftover veggies until I was ready to make homemade turkey stock.
So overall, it definitely saves money, and allows us to eat some excellent quality foods that aren't easily available most of the year, or in small quantities at the regular grocery store.
What I have discovered is that it's too much work organizationally to freeze small bits of this, that and the other. I forget what's in there, and have to put forth extra effort to sift through the random items to figure out what can be used, what's oldest etc.. Now that it's mostly meat and a few specific veg items, it's easy to keep a mental inventory and shop around that, and continually use up the freezer stash.