Rates
Rates describe expenses associated with staffing for an event. Every Event Product Role must have an associated Rate. Remember that Event Product Roles are described like "Violin I for Ceremony for Peter and Polly." When a Rate is attached, it is a function of which Musician is filling the Event Product Role. Once a Musician is determined, then a rate like "Reception Rate for Tom Jefferson" or "Standard Rate for Tom Jefferson" or "Supplement Rate for Tom Jefferson" is applied to the Event Product Role. The 'amount' for Rates determines the amount a Musician is paid for staffing an event.
"If the money don't move then I don't budge" - Lil Wayne
It costs a musician to travel to an event, sometimes they pitch in to efforts that even extend beyond their Role. Often events pay out tips for exceptional performance. Rates therefore do not account for 100% percent of expenses or Musicians' pay, only predetermined amounts for predetermined work.
Once a Rate is created, the 'amount' may not change. In order to account for changes over time, Rates are made inactive 'status' then replaced with newly created replacements. This feature ensures accurate tracking and analysis.