_{I can't get norganna.org/up to work. Did I miss the memo?}
Thanks, RockSlice, for making mention of the API call to query factions and realms other than the one currently being used. Thanks to MentalPower for coding the AucClassic/AucUtil and to Norganna for coding EvalResale I've so blatantly swiped and (in advance) to Dinesh for suggesting a Jira issue (please refer to my adv-114 comment for the low-down).

I feel damn silly for posting this. My original code, aside from comments and eliding, amounts to all of one line:
market, seen = AucAdvanced.API.GetMarketValue(item.link, opposingKey)
And *poof* a new Evaluator. It's so easy to make a new evaluator, and yet I've seen hardly anything. Fine. I'll be the one-line fool who boldly steps out to say "Yes, norgs et al have done such an outstanding job that it really is this simple to extend Auctioneer." I'm hoping that many more will soon follow suit....

About my one-line marvel: It needs much love in the way of usability, but (with repeated runs with tweaked settings), it really and truly shows auctions that provide tremendous opportunities for arbitrage. I'm up eleventy-two gold already. =)

Because I can't figure out what I'm doing wrong with norgana.org/up or pastey.net, code snippage:
-- If auctioneer is not loaded, then we cannot run.
if not (AucAdvanced) then return end

local libName = "Arbitrage"
local lcName = libName:lower()
local lib = { name = lcName, propername = libName }
table.insert(BtmScan.evaluators, lcName)
local define = BtmScan.Settings.SetDefault
local get = BtmScan.Settings.GetSetting
local set = BtmScan.Settings.SetSetting

--{{
-- Obtain the current faction's opposing faction's auction signature
-- Copied from Auctioneer/AucUtil.lua -- junk this once the opposing
-- faction functionality is implemented in Auc-Advanced/CoreUtil.lua
local serverName = GetCVar("realmName");
local factionGroup = UnitFactionGroup("player");
if (factionGroup == "Alliance") then opposing="Horde"; else opposing="Alliance"; end
local opposingKey = serverName.."-"..opposing
--}}

BtmScan.evaluators[lcName] = lib

--{{ --yanked from EvalResale I belive--
function lib:valuate(item, tooltip)
local price = 0

-- If we're not enabled, scadaddle!
if (not get(lcName..".enable")) then return end

-- If this item is not good enough, forget about it.
if (get(lcName..".quality.check")) then
if (item.qual < get(lcName..".quality.min")) then
item:info("Abort: Quality < min")
return
end
end

-- Valuate this item
if (AucAdvanced) then
market, seen = AucAdvanced.API.GetMarketValue(item.link, opposingKey)
end

-- If we don't know what it's worth, then there's not much we can do
if not market then return end

market = market * item.count
item:info("Market price", market)

-- Check to see if it meets the min seen count (if applicable)
if (get(lcName..".seen.check")) then
if (not seen or seen < get(lcName..".seen.mincount")) then
item:info("Abort: Seen < min")
return
end
end

-- Adjust for brokerage / deposit costs
local adjusted = market
local deposit = get(lcName..'.adjust.deposit')
local brokerage = get(lcName..'.adjust.brokerage')

if (deposit or brokerage) then
local basis = get(lcName..'.adjust.basis')
local brokerRate, depositRate = 0.05, 0.05
if (basis == "neutral") then
brokerRate, depositRate = 0.15, 0.25
end
if (deposit) then
local relistings = get(lcName..'.adjust.listings')
local amount = (BtmScan.GetDepositCost(item.id, item.count, depositRate) * relistings)
adjusted = adjusted - amount
item:info(" - "..relistings.." x deposit", amount)
end
if (brokerage) then
local amount = (market * brokerRate)
adjusted = adjusted - amount
item:info(" - Brokerage", amount)
end
item:info(" = Adjusted amount", adjusted)
end

-- Valuate this item
local pct = get(lcName..".profit.pct")
local min = get(lcName..".profit.min")
local value, mkdown = BtmScan.Markdown(adjusted, pct, min)
item:info((" - %d%% / %s markdown"):format(pct,BtmScan.GSC(min, true)), mkdown)

-- Check for tooltip evaluation
if (tooltip) then
item.what = self.name
item.valuation = value
if (item.bid == 0) then
return
end
end

-- If the current purchase price is more than our valuation,
-- another module "wins" this purchase.
if (value < item.purchase) then return end

-- Check to see what the most we can pay for this item is.
if (item.canbuy and get(lcName..".allow.buy") and item.buy < value) then
price = item.buy
elseif (item.canbid and get(lcName..".allow.bid") and item.bid < value) then
price = item.bid
end

-- Check our projected profit level
local profit = 0
if price > 0 then profit = value - price end

-- If what we are willing to pay for this item beats what
-- other modules are willing to pay, and we can make more
-- profit, then we "win".
if (price >= item.purchase and profit > item.profit) then
item.purchase = price
item.reason = self.name
item.what = self.name
item.profit = profit
item.valuation = market
end
end
--}}

local qualityTable = {
{0, ITEM_QUALITY0_DESC},
{1, ITEM_QUALITY1_DESC},
{2, ITEM_QUALITY2_DESC},
{3, ITEM_QUALITY3_DESC},
{4, ITEM_QUALITY4_DESC},
{5, ITEM_QUALITY5_DESC},
{6, ITEM_QUALITY6_DESC},
}
local ahList = {
{'faction', "Faction AH Fees"},
{'neutral', "Neutral AH Fees"},
}

define(lcName..'.enable', true)
define(lcName..'.profit.min', 3000)
define(lcName..'.profit.pct', 30)
define(lcName..'.auct.usehsp', false)
define(lcName..'.quality.check', true)
define(lcName..'.quality.min', 1)
define(lcName..'.adjust.basis', "faction")
define(lcName..'.adjust.brokerage', true)
define(lcName..'.adjust.listings', 1)
define(lcName..'.seen.check', false)
define(lcName..'.seen.mincount', 10)
define(lcName..'.allow.bid', true)
define(lcName..'.allow.buy', true)
--{{
function lib:setup(gui)
id = gui:AddTab(libName)
gui:AddControl(id, "Subhead", 0, libName.." Settings")
gui:AddControl(id, "Checkbox", 0, 1, lcName..".enable", "Enable purchasing for "..lcName)
gui:AddControl(id, "Checkbox", 0, 2, lcName..".allow.buy", "Allow buyout on items")
gui:AddControl(id, "Checkbox", 0, 2, lcName..".allow.bid", "Allow bid on items")
gui:AddControl(id, "MoneyFramePinned", 0, 1, lcName..".profit.min", 1, 99999999, "Minimum Profit")
gui:AddControl(id, "WideSlider", 0, 1, lcName..".profit.pct", 1, 100, 0.5, "Minimum Discount: %0.01f%%")
gui:AddControl(id, "Checkbox", 0, 1, lcName..".quality.check", "Enable quality checking:")
gui:AddControl(id, "Selectbox", 0, 2, qualityTable, lcName..".quality.min", "Minimum item quality")
gui:AddControl(id, "Checkbox", 0, 1, lcName..".seen.check", "Enable checking \"seen\" count:")
gui:AddControl(id, "WideSlider", 0, 2, lcName..".seen.mincount", 1, 100, 1, "Minimum seen count: %s")
if Auctioneer and Auctioneer.Statistic and Auctioneer.Statistic.GetUsableMedian then
if AucAdvanced then
gui:AddControl(id, "Checkbox", 0, 1, lcName..".auct.usefour", "Prefer Auctioneer 4 prices when avaiable")
else
gui:AddControl(id, "Subhead", 0, "Auctioneer options")
end
if Auctioneer.Statistic.GetHSP then
gui:AddControl(id, "Checkbox", 0, 2, lcName..".auct.usehsp", "Prefer HSP instead of Median")
end
end
gui:AddControl(id, "Subhead", 0, "Fees adjustment")
gui:AddControl(id, "Selectbox", 0, 1, ahList, lcName..".adjust.basis", "Deposit/fees basis")
gui:AddControl(id, "Checkbox", 0, 1, lcName..".adjust.brokerage", "Subtract auction fees from projected profit")
gui:AddControl(id, "Checkbox", 0, 1, lcName..".adjust.deposit", "Subtract deposit cost from projected profit")
gui:AddControl(id, "WideSlider", 0, 2, lcName..".adjust.listings", 1, 10, 0.1, "Average relistings: %0.1fx")
end
--}}



also, we know that norganna.org/up and pastey are broken. hopefully fixed sometime soon.

Sorry, didn't get to play. My main computer died last night and the others won't run WoW...
Ah well, hopefully I'll be able to fix it myself!