I just did the first step for Brew Tour 2015. This is the first and only company I called to give us a ballpark.
16-18 passenger party bus
Byob, ice and cups provided. East Cobb pick up
6hr- $932 roughly $55/person
8hr- $1138 roughly $65/person
Tax and gratuity included.
https://partybusesatlanta.com/