The seat is the most important component of any kayak. A comfortable, adjustable seat allows an operator to sit in a kayak all day without fatigue, and it speeds recovery after a long day on the water.
All high-end kayaks have premium seats that have adjustable lumbar support. They are made of coated mesh fabric that drains and allows air to circulate to keep the paddler dry. The best seats, like Hobie and Native, clip into molded recesses and ride securely above the deck.
Below $1,000, you get a decent seat with very limited adjustability.
Entry level kayaks and even some mid-level kayaks have crude seats that are little more than fabric pads or hard plastic pads held erect by cables and straps. A fabric pads sit on the hull. It slides around, and you cannot cinch the straps tight enough to hold it stiff or immobile. A day in one of these seats is a long day indeed. No matter how fit you are, you will experience severe back and neck fatigue.
Also, water pools in the seat area, which keeps the paddler's bottom wet for the ride's duration. This often causes chafing.
Some kayaks have a seat molded into the hull. It provides rigid back support, but again it is impossible to avoid sliding forward, backward and side to side. A molded seat stays wet all day, too. It makes for an uncomfortable experience.