That's exactly what they do. Both should be charged at the same time. For me, my 7% sales tax was the purchase price of the phone + the $30 fee. So not only will I be charge for both, but the sales tax was calculated by combining both of them.My card was charged for $102.10. $72.10 for sales tax which leaves $30 for upgrade. Not sure why but it looks like they did charge me for the upgrade already..
Iphone: $1149
Upgrade Fee: $30
Subtotal: $1179
7% Sales Tax: $82.53...rounded up to $82.60
Total: $112.60 (Sales Tax + Fee)