A trip charge isn't a penalty — it's how you keep prices fair for the customers who live close.
The formula
Take the average drive time to a zone, subtract your target radius (say 15 minutes), and price the extra minutes at your loaded labor rate. Double it to cover the drive back. A 35-minute zone at $50/hr comes out around $35.
Charge by zone, not by call
Customers accept a flat 'service area fee' far better than a per-mile surprise. Publish it by zip code.
Wording that works
"Homes outside our core service area include a $35 travel fee so we can keep prices low for everyone." Waive it for maintenance members.