What term refers to the payment made for professional services where no price is set due to custom or propriety?

The term that refers to the payment made for professional services where no price is set due to custom or propriety is "honorarium." This payment is typically given as a token of appreciation for services rendered, especially when those services are provided voluntarily or in a professional context where standard fees may not be appropriate or established.

Honoraria are commonly used in academia, where speakers may be invited to give lectures or presentations, and instead of a fixed fee, they receive a payment that acknowledges their expertise and time. The concept is rooted in the idea of recognizing the value of the service without imposing a rigid monetary standard, which is particularly relevant in situations where professional practice norms dictate a level of formality in rewarding contributions without predetermined pricing.

In contrast, other terms such as retainer, reimbursement, and commission involve more structured payment arrangements tied directly to services or transactions rather than the more discretionary nature of honoraria. A retainer typically refers to a fee paid in advance for future services, whereas reimbursement pertains to covering expenses incurred in the course of professional activities. A commission relates to a fee paid based on a completed sale or transaction, further distinguishing it from the context of honoraria.