How the Envato format their item pricing ?



Can someone share his view of this pricing formatting ?

Here is the first item with price $15

and the second with price $18

Can someone explain me how the second item has larger price than the first?

If you just go to the details pages of this items - you will see the first plugin ($15) has more features than the second one ($18).

Also, I have one more question - if the author updates the plugin with new features - can this plugin has a new price for this features?