"Mates' rate" is a casual term used to describe a discounted price for friends, colleagues, or acquaintances. It is commonly used in informal settings and can be easily substituted with other synonyms when the need arises. One alternative term for "mates' rate" is "friendship discount," which implies a reduced price offered as a gesture of goodwill. Another term that can be used interchangeably is "buddy price," which is a colloquial expression that communicates a reduced price for someone you are familiar with. Other synonyms include "family discount," "group rate," or "special pricing," depending on the context. Overall, these synonyms provide alternative ways to communicate the same idea of a reduced price offered to individuals due to a pre-existing relationship or connection.