The FAA categorizes skis as plain or combination — plain being straight fixed skis and combination being a ski mounted around a wheel. Combination skis are either retractable or penetration skis. Penetration skis are fixed around the wheel, which sticks out below to allow for landings on pavement. Skis are generally made from composite and metal, but there are also wood skis.
Straight skis are simple, relatively inexpensive (generally below $5,000) and light, but ground handling can be cumbersome at best and the skis take time to install and remove.
Retractable skis provide full flexibility and allow you to seamlessly land on runways, snow or ice. But you can expect to pay between $20,000 and $30,000, and they add a significant amount of weight (100 pounds or more). One exception is the RF8001 from German manufacturer RF-Skis. The complete system adds only 72 pounds, but it is only STC’d for the Aviat Husky.
Penetration skis, like the TrickAir skis above, compromise by allowing for good ground handling on snow and pavement without adding a lot of weight or additional maintenance. The cost for penetration skis varies between $5,000 and $10,000.