Per hour. You can have two hedges 50' long 3' tall. One hedge is trimmed three times a year. Always very little gets cut off for the last cut of the season. May not even need to do a clean if any.
The other 50' hedge has not been trimmer in since last September.
Can't go by size.
Then what if the past pruning has mishapen the shrubs then extra work is time is needed.
Hedge prunning is best to ask an LCO how long it takes them to do job your customer wants done. Then multiply that time by your hourly rate to price out the job.
With experience you will be able to judge the time needed. Remember because you don't have the best suited eqiupment and the job takes longer you can't expect the customer to pay you for the extra time it takes you.
That would be like trying to charge someone 10 hrs to do their lawn with your 20" mower that another LCO can do in 1 hr with their 60" ZTR.