My partner and I share a T-Mobile plan...$80 per month (total), unlimited minutes, unlimited text, very limited data (500 MB or something).
We've looked for more economical options, but this is what's worked out best for us given our usage (and without having to buy new phones). I use LOTS of minutes talking to elderly parents in another state, and my partner's teenage kid (also in another state) only knows how to communicate using text. My partner also likes that I have a cell phone for when I take bike adventures by myself or have to go out of town for work.
On the bright side, our phones are almost four years old...and we don't plan on replacing them until they fall apart!