OK. Found another piece of preorder figures data.
Aliens: Colonial Marines.
Apparently this game was a piece of ***, but it sold 1.31 million copies in part thanks to preorders.
However, the class action lawsuit related to it shows that preorders were not enough to actually earn the devs any money (look for Pitchford's talks or this summary here:
https://www.vg247.com/2014/08/01/aliens-colonial-marines-no-royalties-says-gearbox/). I unfortunately couldn't find out how many sales were preorders.
Now, Gearbox did get a shoddy product out the door. They also used the money on other projects (Borderlands), thereby lying/mishandling the paiments done by Sega. In the end, they respected their contract but not the spirit, delivered a poor game, and got no bucks for it in the end. Sega screwed by not cancelling the project when they found out they'd been cheated by Gearbox. People who preordered were screwed by the bad game, but the company didn't make any benefit off it, and one of the codevelopers went bankrupt.
Sega nevertheless pushed out 4 DLCs over 5 months after release, so the game did get some support after release, and the DLCs seem to be good, contrary to the released game.
What to learn from this?
1/ Definitely don't preorder from companies you don' trust. I would say that the developper is more important than the publisher here. For instance I trust Firaxis more than 2K, and Sega more than Gearbox (which is saying a lot about the latter).
2/ The developper didn't get any financial benefit from preorders. Nor did they lose money. They were paid on milestones, and the preorders didn't amount to enough sales to bring them any royalty. So in this case, claiming that preorders help getting shoddy games is wrong as far as the developper is concerned.
3/ I lack data about why Sega didn't cancel the game in 2008 when they should have (Gearbox cheating on them). Did they have enough preorders 5 years before release that cancelling would have been a net loss? I doubt it. Did they get enough preorders to make up for the bad press later? Maybe. I think they hoped they would still get something for their money and the franchise could sell. Did they hope the preorders would bring enough money by themselves to make up for 5 years of development? Maybe, but I find it hard to believe as the net result was that the game didn't make enough money to pay royalties to the develeopper, so it was a failure for the publisher too. They probably cut some of their losses with preorders.
4/ Lawsuits are good, as they allow to get some data.
Now, based from this, should we never preorder anything?
I still think no. If you trust the developper, I see no reason to refuse giving them money early. That's mostly kickstarters/indies. I guess the relationship between Paradox and Obsidian might be that way, but it's impossible to know for sure.
For big developpers, it's likely Firaxis gets contracted and so has a budget which is independant of preorders. In this case, preorders will get the developper nothing, so it's not supportingthem.
Big developpers like CDprojekt may be quite different (I mean, they're working with GoG, not Steam or major publishers).
So what is the risk/reward?
- developper cannot be trusted: High. Don't preorder.
- developper can be trusted but has a big publisher behind them: Preorder won't help them. Don't.
- same case but preorder actually brings something (reduced price, preload, early access to Aztec DLC): if you're in a hurry, you may, but you're taking a bit of a risk
- same case but preorder brings something exclusive (DLC you won't ever be able toget otherwise): your call. I think it's an evil practise unless the thingy is just cosmetic.
- developper can be trusted and is indie/will get funds for backing, like kickstarter: you're taking a risk, just know that you're taking a risk. If not for kickstarters, I wouldn't have played Pillars of Eternity, so it's worth taking risks.
If enough people preorder a game, does someone else risk getting a worse game because of it?
I think no. They just risk getting no game at all if the game is cancelled.