It would be nice for the Technicians to have the ability to change only specific Service Item Prices.
Vote for COMMUNITY-I-1870 idea if this is something you would like to see!!
I like that you can set the parameter that they can't change any price in the book at will, however, it would be nice to allow for individual service items to be changed. This can be as simple as a checkbox on the item when entering the item in the pricebook of "Allow Technicians to Change Price".
That way when a customer estimate is needed, for a one-off job/repair, the technician can add that specific line item and then input a price and summary/description.