WoWInterface - Vendor Cost of Item

I can't figure out how to get the cost an item sells for at the vendor.

I've through the code of SellValue, Informant, etc and can not figure it out. I've got my mod to loop through my bags and sell every grey item, but I can't figure out how to get the price. Being able to check for certain grey quest items would be nice (e.g have no sell value).

Code:

function Minimalist:MinSellJunk()

  local bag, slot, sellprofit

  for bag = 0, 4 do

    if GetContainerNumSlots(bag) > 0 then

      for slot = 1, GetContainerNumSlots(bag) do

        local _, _, _, quality = GetContainerItemInfo(bag, slot)

        if (quality == 0 or quality == -1) then

          if (self:ProcessLink(GetContainerItemLink(bag, slot))) then

                        sellprofit = sellprofit + X

            PickupContainerItem(bag, slot)

            MerchantItemButton_OnClick("LeftButton")

                  end

        end

      end

    end

  end

  self:Print("Total Sold Item Value: "..abacus:FormatMoneyExtended(sellprofit))

end

Basically, I need something to replace X.