A cheap switch and an expensive switch will both turn a light on, but fixtures that draw more power require the larger, more durable parts built into the expensive switch.
More expensive switches are necessary for the larger power demands caused by multiple lights or large motors.
Switch heavy loads with the $2 switch. The contact area is twice that of the 39¢ switch, and the spring arm is heavier, so you'll replace them less often.
Home centers sell 15-amp light switches for 39¢ in bins, and 15-amp switches in boxes for $2. They'll both do the job, but the $2 switch has a beefier spring arm and larger contact surfaces. If you're just switching a few room lights, the 39¢ switches work fine and will last a long time. But if you're switching 10 or 15 recessed lights or a large motor (like a ventilation fan), or the switch gets used dozens of times a day, pick the $2 switches. They'll last longer.