The core mechanic: fixed costs in a “per-person” world
Many travel products have fixed costs that do not drop when one person travels instead of two. A room still needs to be cleaned. A guide still runs a tour. A vehicle still moves.
When a product is priced as “per person,” those fixed costs are often implicitly split across two people. If one person occupies the same “unit,” the pricing model either absorbs the shortfall or passes it to the solo traveler.
Why “single supplement” appears
A single supplement is a mechanism to keep revenue per unit closer to what a business expects when the unit is designed for two.
It is most visible in:
- hotels (double rooms as the default inventory)
- tours (shared rooms as the base assumption)
- cruises (cabins priced on double occupancy)
Why the same trip can look inconsistent
Pricing often depends on:
- inventory constraints (how many single rooms exist)
- seasonal demand (ability to sell the room to two people)
- packaging (whether the operator buys blocks of rooms)
This is why solo pricing can feel arbitrary even when it is not intentionally targeted.
A useful mental model
When you see a single supplement, translate it into a question:
“What is the unit here, and how is the cost of that unit normally distributed?”
That one question explains most of the pattern.