The code guide I (will, eventually) share will absolutely show invoice price.
Then, each customer signs their POC that shows invoice and normally shows holdback as well (which sometiems the system blanks out, but it is 3% of MSRP not including destination).
I think what you mean is that you don't know the full cost, and full revenue, associated with the specific transaction.
Well that's true. In fact, we don't know exactly, because a lot of the costs and revenues end up being spread out over multiple vehicles over the course of different volumes/spans.
For us, it's about probability in that with enough volume, those costs vs revenues will make it a profitable endeavor. Not by much, but at a small margin per average vehicle.
Do it a lot, and that multiplies out quite nicely. Our owner says the car business for us is not a marathon, it's a track meet. There's a LOT of different things happening at once, and you don't have to win every event by a landslide to win the whole meet. We find revenue, and savings, where other dealers aren't looking. We pass as much of that savings as we can on to the customer, where appropriate - and then y'all tell a friend.
In short, the invoice IS what we pay for that specific vehicle - and EVERY dealer pays the same invoice. But just like the invoice for a restaurant on how much they pay for ground beef isn't their entire cost of getting the burger on the bar, they've got to wash the dishes. They also make money on the beer. If you buy enough beer you get free baseball tickets, and enough burgers and you get a credit for cases per delivery average metrics too. But the burger invoice is what is, in terms of cost of goods sold from an accounting perspective.