My mobile phone usage various considerably, but, mostly I don't use it on a daily basis. I transferred my Moto-G from Verizon to BYOwireless.com. My basic monthly fee is $5 / month. Doesn't include much 100 minutes and 100 texts. But for $15 you can add 1GB of data (and add-on plans starting at $5).
Since I use Google Voice, I don't get dinged for a single text message sent/received on my phone. When my 'voice' minutes are exhausted, I use "Hangouts" to place and receive calls over WIFI or 3G. Yes, I'm limited to about 4 or 5Mbps with 3G, but I don't care because I don't need more (Navigation, voice, text, low-data-use apps, etc.).
So, $5 a month (plus Google Voice/Hangouts services) gets me unlimited voice, text, and 1GB of data. Now, for me, that's a great deal. Occasionally, I will add $5, $10 or $15 for extra data services, when I need to travel. Typically, Five Bucks a month does it for me. My annual cost might be $100-$120 a year.