Your Success Manager should be able to assist in understanding Pricebook utilization within a given period. I would suggest reaching out to them to run the "Pricebook Utilization Query in SQL" and they'll be able to provide an excel file denoting how many times within the given period each service/material/equipment has been used.
On the other end of the question, an invoice-items report will help understand what is currently being used/consumed on invoices while providing information at the item-level granularity.
A frequency report would be a really good thing to have. I sometimes will deactivate a task that is not used by my team except for one tech a few times a year. But that might be good enough to keep the item!