mini with cellular + voip software + earbuds or headphones with microphone can be a GREAT alternative to an iPhone with a monthly cellular bill. In my case, I have Comcast Voice at home. They have an app too. Shockingly, it's a pretty good VOIP app, which "rings" my Mini whenever anyone calls the home number. I can also call from it and text to anyone (and receives texts from anyone).
My cell phone needs for voice have always been sparse so this works well. To pinch costs further, I use the AT&T 3 month or 1GB data plan on the cellular side. At $25 for 3 months, it covers my needs anytime I'm out of a wifi zone. Often I can let it lapse for a while since I'm typically in wifi zones. So for 2 or 3 payments of $25 during an entire year, I feel like I'm not missing a thing in terms of cell phone benefits.
There's lots of great VOIP apps in the store, so try a few and find one you like best. This is an especially good option for those who use their phones mostly for texting & internet vs. voice (though it covers voice just fine). Instead of about $40 to about $120 per month (depending on plan and carrier), about $50-$100 can cover cellular service needs for an entire year, saving somewhere between about $380-$1340 every year.
Now, if you are someone constantly talking on a cell phone, you may find that an iPhone is a better option. It takes a bit more effort to take & make calls when you can't just hold your "phone" up to your ear. But otherwise- and especially if one tends to be carrying both phone and tablet around most of the time- it's a pretty good alternative that does save a lot of money.