But also, what kind of machines are you using? a lot of the pro shops and specialty shops charge more because of the top of the line machines they use.
A lot of this just depends on your area. If there is a lot of competition, then prices will be low, if there isn't then prices will be high.
Also, some of the people here say they can do it in 10-15 minutes. That is a tournament stringer doing a super rush job. If you can mount, open the string pack, string the racket, tie off, cut excess and straighten out the strings in 10 minutes, then hats off because even the speed stringing contest, the guy who won did it in 11 minutes. To say that you as a home stringer can do it faster than guys on top of the line electric, I find that hard to believe. 15, believable, 10.. not so believable