Book a tour or a cruise on your own, and you’ll run into a charge that shows how the industry sees you. It’s the single supplement, and it means you pay more, sometimes much more, for the crime of not being a couple. The fee ranges from 10% to 100% over the standard rate. On cruises, paying double for a cabin meant for two is normal.

The bookkeeping is real. Operators price a room for two, splitting it, and an empty second bed leaves a hole. But that is a decision, and a revealing one. For years, the industry priced around couples and families, leaving the solo traveler to cover the difference. The supplement tells you exactly how the industry has traditionally valued solo travelers, and the number is low.

The rollback is uneven

Solo travel is a $482 billion market, and the industry is discovering these travelers and walking it back. Some of that is real. A few cruise lines build solo cabins for one, and some operators set a flat, modest supplement. But much of it is show: short promotions, cabins that sell out fast, and “no single supplement” deals with a higher base price. Even some of the companies that pioneered solo cabins haven't expanded them as quickly as demand might suggest. For most trips, you pay as if the trip were sold out when it isn’t.

What a fair price looks like

There's a legitimate argument behind the fee. On a sold-out departure, a solo booking really does cost a fare—the second traveler who’d have taken that bed—and a premium is fair. But tours and cruises rarely sell out, and the supplement gets charged flat, as if they all did. When a space would have sailed empty, a solo guest at the single rate is found money. It’s why waivers cluster at the last minute and in the off-season, when the empty-bed excuse falls apart. A fair supplement would track occupancy: smaller as a trip fills, gone on the empty ones, shown in the first price you’re quoted.

What you can do about it

Your power here is real, even when it doesn’t feel like it. Ask what the supplement is before you book. Walk when it stays high on a trip that clearly hasn’t filled. Spend with the operators who set the price of the room you sleep in. Money following the fair players is all that’s ever moved this industry, and solo travelers are now big enough to move it. We should act like it.