How much is total bill for Go Phone prepaid $45 plan?

I am a postpaid customer with At&t and was recently reviewing GO Phone prepaid plans and saw they have a plan for 3gb of data/unlimited talk/text for $45/month. However, would this be the actual total cost plus tax, OR is there an additional $20 charge for the phone device, similar to the postpaid plan? Basically I am asking whether my final prepaid bill would be $45 plus tax, or $65 plus tax??