My Kingdom for your entertainment system

Why do they always do this to us? You take home your entertainment device, hook it up to the tv, just to find out you can't hook it up to the TV because you're missing a part that's not included in the box. So you run down to the store to pick up said missing part, and it's like $30 bucks! It's a few wires and a button, why is the god damned thing $30?!