Most service pricing is conditional: this much, unless it is that, in which case add this. Price rules let you write that down once.
Conditions, Then a Price
A rule matches on the conditions you set — service, option, customer type, data field — and applies the price or adjustment you specify.
Surcharges and Discounts as Rules
Surcharge and discount rules are separate from base pricing, so a seasonal adjustment does not mean editing every price in your list.
Fewer Combinations to Maintain
One rule replaces the rows you would otherwise write for every combination, which is what keeps a price list changeable.