Most suppliers will offer 3 levels of badminton post, a schools model which will be very basic and usually to a lower specification to regulation, a club model that can be used for amateur competitions within clubs and leisure centres, and a competition model that meets the standards needed in the professional games.
As with any nets, the thicker the twine, the longer the net will likely last. Most suppliers will offer a basic 1mm thick net and a heavy duty 2mm net.
Range in quality depending on the users requirements. The better rackets will be made from lighter materials to move the racket quicker through the air to generate increased power.
Again range in quality depending on the level of game being played. Professional players require the shuttlecock to fly true through the air to maintain performance whereas an amateur player doesn't expect or need this level of performance so a lower quality shuttlecock can be used.