The line items people forget
Driver wages are the obvious cost. The ones that surprise retailers are dispatch labor, insurance, vehicle maintenance, training time, coverage for callouts, and the management attention that delivery quietly consumes every week.
A fleet is not a line item. It is a department with its own hiring, scheduling and failure modes.
How to compare honestly
Compare total cost to serve a delivery, not hourly wage to per-delivery fee. Include the hours your managers spend on the operation, and the cost of the weeks where volume does not fill a shift.
When building internally makes sense
Consistent, high daily delivery volume in a tight radius, with management bandwidth to run it, can justify an internal team. Below that threshold, a partner usually absorbs the volatility better.