The fare according to Travelocity is $49 plus taxes and fees total $69. Travelocity includes a $5.00 service fee (which I think is a Travelocity booking fee). Also for some reason there is another $5 hidden in there.

I had this same issue when I booked SLC-DEN on F9 price was $59.30 on Frontier's site but $69 on Travelocity. I booked with Frontier and my credit card has only been charged $59.30

So I think that you paid $10 more via Travelocity ($5 travelocity booking fee and $5 fee from Frontier for telephone and travel agent bookings).

I could be wrong about the $5 frontier fee but I thought I read that on this board, however I thought it was only going to start today.