We don't know how far he drove or how rural this area is. Let's assume that the customer is 90 minutes away from you and you are guessing 1 hour of work, and that before you show up, you really have no idea how long you will be there.
That is 4 hours minimum that you are out for this job, and possible 5-6 since you haven't seen it yet if you were to run into move complex wall issues.
Would you REALLY give a firm quote of $100 for being out 6 hours, effectively making just over $10/hour? Or would you make it significantly higher due to distance and unknown's?
Keep in mind that the quote was agreed upon before the work was done and most likely before anyone even looked at the job. Tons of unknowns at that point.
How far did the tech drive to get there? 30 minutes? 90 minutes? Double that for round trip.
Also, depending on the state, up to 10% of that could be sales tax.