T-mobile prepaid to go: 10 cents/min.    Good for those who use phone infrequently.

Spend $100 to qualify for gold member, gold member minutes won't expire in a year. Next year before minute expires, refill as little as $10 and you can roll over all the remaining minutes for another year.

I have this phone for parents's use during their visiting. Had it for 2 years now and total cost is $120. still have more than half of the original minutes left.  If the minutes last 4 years then the average cost would be ~$3 per month.