tutorial/Buy and sell items

First of all, read the economy tutorial and the commands tutorial.

Give money to the player with COMMAND: 'givemoney: <number>'.
Take money from the player adding PRICE: <number> to an icon.

Give items with COMMAND: 'give: <id>[:data],[amount]'
Take an item adding REQUIRED-ITEM: <id>[:data],[amount] to an icon.

Sell items

The example below sells a diamond to players for a cost of 100 money.

      COMMAND: 'give: 264'
      PRICE: 100
      NAME: 'Buy a diamond'
      ID: 264
      POSITION-X: 1
      POSITION-Y: 1

Buy items

The example below takes 64 dirt from the player and gives him 10 money.

      COMMAND: 'givemoney: 10'
      REQUIRED-ITEM: 3, 64
      NAME: 'Sell dirt'
      ID: 3
      POSITION-X: 1
      POSITION-Y: 1