It actually appears to be showing the unit price divided by the quantity. Digging through the code, I've decided that I simply don't understand lua. In addition to that though, I can change this line in core.lua:

118 local price = record.unit_price * (listing == 'bid' and record.stack_size / stack_size_slider:GetValue() or 1)

to

118 local price = record.unit_price * (listing == 'wtf' and record.stack_size / stack_size_slider:GetValue() or 1)

and I will get the correct auction bid prices on the Post tab. It doesn't help when I click on it though. It still populates my unit starting price with the wrong value.

I'm still looking at it, but my lua sucks.

It's meant to be this way. It shows the stack price, not the unit price, divided by your selected posting stack size, i.e., the pseudo-unit price that you would be undercutting (because actually you're undercutting the stack price, that's the whole point of the bid listing, undercutting stack bid prices so you appear higher up in the sorting of the default blizzard AH which can only sort by stack bid prices)

Yes. That's what it supposed to be doing, but that's not what's happening. For instance. When I try to post an Auction of heavy stone, the Post tab shows the cheapest bid at 23c/unit. When I look at the Blizzard pane (or even the Aux Search Pane). the cheapest bid price is actually 2s87c/unit.

The bid (per/item) values are different between the Post tab and the Search tab. The search tab is correct, because it correlates with what I see in the Blizzard UI.

That's because the stack size is different. If you have a larger stack size you need to undercut a lower pseudo unit price to undercut the stack price. That's why it's divided by your selected stack size, not by that auction's stack size.

let's say there's an auction of 1 murloc eye with bid price 10c. You wanna post an auction of 10 murloc eyes. That auction's unit bid price is 10c, but in order to undercut its bid stack price with your stack size of 10 you need to have a unit price of less than 1c or in other words you need to undercut the "pseudo unit price" of 1c which is what aux is showing.

I think I finally see the logic problem here.

It looks like it's taking the AH price, dividing it by MY stack size, not the AH stack size for the same item.

In my case, I have 12 [Heavy Stone]

The cheapest AH bid price is currently a 1 item stack (not really a stack) for 2.87s

On my Post page, it grabs that 1 item stack and divides it by my 12 item quantity so it wants to set my unit bid price to 23c when it should be setting it to 2.86s - one copper less than the price of the cheapest unit price on the AH.

Yes, that's how it's supposed to be!

Why does the slider change the Auction bid (per item price), but not the Auction buyout (per item price)?

Because with the buyout you wanna undercut the unit price and with the bid you wanna undercut the stack price. And to undercut the stack price, the higher you set your stack size, the lower you need to go with the unit price.

I love your addon man. I really appreciate your responses too. I would much rather be playing the game that writing code, so I know it takes a lot to do what you do.

Thanks. Note that I'm aware this feature can be rather unintuitive (and it is disabled by default).
It's a very specialized feature meant more for increasing the likelihood of people buying your buyouts than having much to do with bidding.

Since it was posting my stuff orders of magnitudes cheaper than the next lowest cost item on the AH, I forked the code and applied a couple changes that made it behave more along the lines of the way I wanted it to behave. I need to work on the sorting though.

Well it doesn't automatically price anything. The prices in the bid listing are to be seen more as a warning than as a recommendation. The listing is sorted by stack bid price, so the same order as the auctions will appear in the blizzard auction house when using its limited price sorting. The position of the item in the listing you undercut corresponds to the position your auction will have in the AH, and the pseudo unit price tells you how low a unit bid price you need to risk in order to "buy that position".

It doesn't really give you the price in the AH. It gives the cost of the cheapest item in the AH - then it divides it by the number of units I want to sell. The numbers don't really have anything to do with one another.

If there is 1 Gold Bar in the AH for 90s/1G, and I want to sell one of mine, it tells me the cheapest undercut price on the AH is 89s/99s per bar. That makes sense to me.

Now, if I want to sell 10 of mine, it tells me the cheapest undercut price on the AH is 8s/99s per bar. That's a huge discount - 80s for a whole stack of Gold?

If I want to sell 20 Gold Bars, it gets better. Aux tells me the cheapest undercut price is 5s/99s per bar.

It doesn't just tell me that, it actually posts my auction bid price on 20 bars of gold for 1G for the whole stack.

Now that I changed a couple lines, it will use the price at 89s/99s per bar, no matter how big my stacks are.

I just have to believe that I'm completely off base here and am missing the whole point. It wouldn't be the first time; I argue with devs for a living too.

You're missing the point. Like I said, the bid listing is not meant for bidding. (though even the "real" bid price of auctions should never be used as a price indicator because it may start way below the market value and the poster can always cancel so there's no risk in posting "fake" low bids)

You should use the buyout listing as an indicator for the value (besides aux' historical value, which is also based only on buyout values) even for your bid price choices.

The only purpose of the bid listing in aux is to help you undercut stack bid prices which helps you trick people into buying your buyouts even if they're not the cheapest because they will appear at the top of the price sorted default blizzard AH.

There are 50 auctions per page and the default AH only shows like 10 or something at a time. Most people will not bother manually checking all prices, let alone doing that for multiple pages. They will use the best assistance the default AH can provide them: sorting by bid stack price. That's the only price sorting there is in the default AH. Then they will likely assume that the correlation between bids and buyouts is mostly linear and that the lowest bids will also have the lowest buyouts. But by setting your bid very low with a high buyout you can make your auction appear at the top of that listing and anyone who doesn't bother scrolling through all 50 auctions of the page and carefully checking may buy your auction at an inflated price.