A used 20HC side-door container is two scarcities multiplied together. The 20FT High Cube is already a thin production type that carriers rarely reposition, and side-door equipment is built to order for specific users who keep it rather than release it. Almost none of it reaches the used market, so the few units that do are priced on scarcity rather than on condition.
Start with the 20FT High Cube, which is produced in short runs and rarely repositioned, so it barely accumulates as depot surplus at all. Then add side doors, which turn a standard box into purpose-built equipment ordered by a buyer who has a specific loading problem.
Each factor alone thins supply. Together they remove it. A used unit combining both is not a market with a price, it is an occasional listing.
Depot surplus comes from carriers, and carriers own standard dry containers because that is what their fleets are built from. Side-door units are almost always shipper-owned equipment bought by a warehouse, a manufacturer or a project operator for a reason that has not gone away.
Equipment bought for a reason stays with the reason. When it is finally released it usually goes directly to another user in the same trade rather than into a depot yard where anyone could find it.
When a used 20HC side-door does appear, its price reflects availability rather than remaining life. You are frequently asked to pay close to, and sometimes above, the cost of a new factory-built unit for equipment that has years of service behind it, unknown door alignment history and no guarantee.
Side doors are the part that wears. Hinges, locking bars and the full-length gasket run take load every time the unit is opened, and a used side-door unit with tired hardware is expensive to put right.
A new build gives you the current specification, a warranty period, aligned doors and a documented unit. Against a scarce used unit at a scarcity price, that comparison is usually not close.
The trade-off is time. A factory order runs against a production month and is delivered on a first trip, so it is a plan rather than a purchase you can complete this week. Specifications are on the 20FT Open-Side page, and Guide 13 covers what delivery involves.