Custom Prices v1

=begin
===============================================================================
Custom Prices                                                     Version 1.0
by KK20                                                           [11/25/2013]
===============================================================================
_______________________________________________________________________________
+ Introduction

 RPG Maker only allows items to have one set of prices. The sell price of items
 is half the price set in the database. With this script, you can modify the
 prices of items, weapons, and armors to whatever you want. The change is only
 temporary, so you can have shops sell certain items at unique prices. You can
 also change the sell price to anything. Make an item cost a high amount, but
 make it unavailable to sell. Have shops buy specific kinds of items. The
 choice is up to you!
_______________________________________________________________________________
+ Instructions

 Place this script below any custom scripts that rely on item prices.

 To change the prices of items, use one of these script calls:

        price(TYPE, ID, BUY_PRICE)
        price(TYPE, ID, BUY_PRICE, SELL_PRICE)

  where TYPE can be 0 (Item), 1 (Weapon), or 2 (Armor)
        ID refers to the item's ID in the database
        BUY_PRICE is the new price of the item
        SELL_PRICE is the new sell price of the item
        SELL_PRICE is optional. If you do not put a sell price, items will
          default to being half the BUY_PRICE.

  If you ever need to reset the price changes, use the script call:

        reset_prices

  This is only needed if using custom scripts that rely on item prices
  but are not considered shops (e.g. ForeverZer0's Blacksmith Shop).

  -------------
  Examples:
  -------------

  price(0, 1, 300)              # Potion prices: BUY = 300, SELL = 150
  price(1, 1, 5000, 100)        # Bronze Sword prices: BUY = 5000, SELL = 100
  price(2, 25, 9001, 0)         # Ring of Strength prices: BUY = 9001, SELL = Can't sell at this shop
_______________________________________________________________________________
+ Notes

 It is recommended to put these script calls just before the 'Shop Processing'
 command. Immediately after the player exits the shop, the item prices WILL
 revert back to their original database prices.

 This script may be compatible with some Custom Shop Systems. The more complex
 the script, the less likely.
_______________________________________________________________________________
+ Credits

 KK20 - for writing the script
 firevenge007 - requester

===============================================================================
=end

#==============================================================================
# ** Interpreter
#------------------------------------------------------------------------------
#  This interpreter runs event commands. This class is used within the
#  Game_System class and the Game_Event class.
#==============================================================================
class Interpreter
  #--------------------------------------------------------------------------
  # * Set new item prices temporarily
  #--------------------------------------------------------------------------
  def price(type, id, buyp, sellp=buyp/2)
    case type
    when 0
      $game_temp.changed_prices.push([$data_items[id], $data_items[id].price])
      $data_items[id].price = [buyp, sellp]
    when 1
      $game_temp.changed_prices.push([$data_weapons[id], $data_weapons[id].price])
      $data_weapons[id].price = [buyp, sellp]
    when 2
      $game_temp.changed_prices.push([$data_armors[id], $data_armors[id].price])
      $data_armors[id].price = [buyp, sellp]
    else
      return false
    end
    return true
  end
  #--------------------------------------------------------------------------
  # * Revert items back to their original database prices
  #--------------------------------------------------------------------------
  def reset_prices
    $game_temp.changed_prices.each{|item|
      item[0].price = item[1]
    }
    $game_temp.changed_prices.clear
  end

end

#==============================================================================
# ** Game_Temp
#------------------------------------------------------------------------------
#  This class handles temporary data that is not included with save data.
#  Refer to "$game_temp" for the instance of this class.
#==============================================================================
class Game_Temp
  attr_accessor :changed_prices, :sell_flag
  #--------------------------------------------------------------------------
  # * Initialize two more variables
  #--------------------------------------------------------------------------
  alias init_changed_item_prices initialize
  def initialize
    init_changed_item_prices
    @changed_prices = []
    @sell_flag = false
  end

end

#==============================================================================
# ** Various RPG classes
#------------------------------------------------------------------------------
#  Redefine item prices to have individual buy and sell prices.
#==============================================================================
class RPG::Item
  def price
    if @price.is_a?(Array)
      return ($game_temp.sell_flag ? @price[1]*2 : @price[0])
    else
      return @price
    end
  end
end

class RPG::Weapon
  def price
    if @price.is_a?(Array)
      return ($game_temp.sell_flag ? @price[1]*2 : @price[0])
    else
      return @price
    end
  end
end

class RPG::Armor
  def price
    if @price.is_a?(Array)
      return ($game_temp.sell_flag ? @price[1]*2 : @price[0])
    else
      return @price
    end
  end
end

#==============================================================================
# ** Scene_Shop
#------------------------------------------------------------------------------
#  This class performs shop screen processing.
#==============================================================================

class Scene_Shop
  #--------------------------------------------------------------------------
  # * Main Processing
  # Reverts item prices back to their database amounts when closed
  #--------------------------------------------------------------------------
  alias revert_item_prices_after main
  def main
    # Calls main/default method
    revert_item_prices_after
    # Revert all items back to their original prices
    $game_temp.changed_prices.each{|item|
      item[0].price = item[1]
    }
    $game_temp.changed_prices.clear
  end
  #--------------------------------------------------------------------------
  # * Frame Update (when command window is active)
  #--------------------------------------------------------------------------
  alias update_sell_flag update_command
  def update_command
    # If C button was pressed
    if Input.trigger?(Input::C) && !Input.trigger?(Input::B)
      # Branch by command window cursor position
      case @command_window.index
      when 0  # buy
        $game_temp.sell_flag = false
      when 1  # sell
        $game_temp.sell_flag = true
      end
    end
    update_sell_flag
  end
end