One visit, the whole wall list
Most people have more than one thing to hang. Put every item in one request: the blinds in the bedroom, the mirror in the hall, the towel bar in the bath. Each one gets its own price.
What decides the price
How many items, how high they go, and what the wall is made of. Plain drywall with studs is the simplest. Plaster, tile, brick and stone take different anchors and more time.
Before the pro comes
Have every item out of its box with its hardware, and mark where you want things to go with painter's tape. The pro checks for studs and pipes before drilling.