What are custom foot beds?:

Ski boot foot beds are inserts (orthotics) molded to bring the load bearing parts of the foot in sync with the gravitational force of the skeletal system. This is often compared to how the foundation (feet) of a house carries the weight of the house through the studs (bones) in the walls. Ski boot foot beds are molded from a semi-rigid material which distributes the forces developed on the foot during a ski turn.

This relieves the soreness and fatigue that foot abnormalities can cause.

I bought expensive ski boots. Why would I also need custom foot beds?:

Off-the-shelf ski boots are hardened outer shells with soft cushiony liners. The cushioning actually allows the foot to move in the shell during the leg action while skiing. This, in turn, dissipates the exactness the leg needs to communicate to the ski through the foot and ski boot. A custom foot bed stabilizes the foot within the boot and provides for a more direct and efficient transmission of the leg muscle action to the foot.

How much do custom foot beds cost?:

There are different types of foot beds and since they all start from some sort of base material they can pretty much be called custom foot beds. Some are pre-cut to shoe sizes and then are heated while your foot makes an impression. Others are much more involved using different techniques to make a mold from a raw base form. The cost can range from about $40 to over $200, depending on how labor intensive the process is and the composition of the blanks.

Custom Foot Bed Fitting:

How to decide if you need custom foot beds, how foot beds are measured and made, as well as information on where to get them:
Custom Foot Bed Fitting - Instaprint
Custom Foot Bed Fitting - Surefoot