Our minimum service charge is $180. In 1 year we went from $140, to $160, to $180. Figuring it out as I go. I worked for a customer that lives about 300 yards from us and told her I'd do the job for $160 since there is hardly any travel time, but she insisted on giving us $180. I think next year I am bumping it up to $190. It covers a little more of our expenses and doesn't hit the daunting $200 mark.
The furthest we travel for any job is about 45 minutes. On most days I have been able to line up other appointments close enough in proximity on the same day to make it make sense without having a higher minimum charge for those folks. Although sometimes it doesn't work out that way, maybe I should fix that.