I had $3 worth of fun, watching the sun set ;).
Seriously - I find it hilarious to measure fun in cash...
On topic - let's find a middle ground, shall we ? $3.99, $7.99 and $12.99.
$3.99 for the true oldies that can't be bundled and, frankly, are too expensive at $5.99.
$5.99 for older-but-not-THAT-old titles
$7.99 for the titles that get priced at $9.99 just because $5.99 is too low. $7.99 also becomes our sweet-spot, the middle price-point and a fair trade-off between "meh, $9.99" and "OMG, $5.99".
$9.99 for newer/better/really popular titles
12.99 for newest games +/- their expantion packs (notice that we never buy these separately for a reason... Every GOG should be a platinum-GOTY-full edition, so we don't have to buy anything else to enjoy the title with all the patches, features etc.).
$12.99 also becomes a useful negotiation tool. Imagine the GOG game-getting team contanting WotC and asking them for permission to release Planescape: Torment on GOG. WotC guys might go "no way - screw you guys. Get off our D&D lawn !"... However, if the GOG guys had the possibility to say "What if we gave you three bucks from every copy ?", they might be greated with a (luke)warm "Now THAT sounds like a pretty good deal. Where do we sign ?".
Three bucks above $9.99. Think about it.
As for $9.99 being abused in case of a higher option - I can't make a better argument than remind you that we still have a lot of games priced at 5.99, despite their ridiculous popularity and high value. And I'm not even going to say "Arcanum" - I'll say "Fallout 2".

There's little they can do under pressure from publishers. I trust them, but it's not like they have much of a choice if they want their back catalog.

Slippery slope. "Okay, we want 4 bucks extra." says the next publisher. You get the idea. It's important to stand your ground now and not give in. Of course publishers are going to ask for more money. That's a given.

They are dealing with publishers for 14 years and I think they know way better than us how to negotiate with them and what are the best price points.

I'd have no problem with a 15 dollar price point if there are some serious requirements for the game to get it. Ubisoft already leapt upon the 10 dollar price point for game which would should have been 6. Let's try to avoid that.

But that's just it, there is much they can do and have already done. They can refuse to carry a game if the publishers demand too much. Their philosophy has always been to give us the best value for the dollar, if what the publishers demand does not equal that, then they just won't sell it. Its the publisher's loss. They don't get any sales from the old game and people without any legal means of getting the game at a reasonable price will continue to pirate it. GOG has the high ground here, not the publishers.

I think it's important to question decisions, whoever makes them. Or else this whole thread would be moot.

How do you know Ubi was the one who decided that their games should be $9.99? It could easily have been GOG's decision, with the expectation that they were worth that.Considering that is what they sell for on the discount rack in my local stores, that's not really surprising. I would guess (and this is clearly only my opinion) that those are some of the worst selling games on the site. Consider it a lesson learned, no matter whose decision it was to mark them at that price.

Do they? Activision has a large back catalog of old games. GOG caters in these things. They want them. And in the interviews they even state that they will make concessions, they will put 'not good-bad' games for sale if its in the deal with the publisher. Why wouldn't they make concessions in this case?

Maybe Ubisoft wanted to compensate with HoMM1 for the HoMM3. We will never know what discussions were in between. :)
I believe that GoG has all the interest to maintain the prices low in order to make good sales and promote the service. So if they can't get lower with the price it must be for a reason. I prefer to have a game released at a higher price than not to see it released at all.

Because they already have done that and said as much. There is always going to be some compromise, that is the nature of the business, but that doesn't mean the kowtow to the publishers every whim and demand. If what a publishers asks is too much or they don't offer enough, then they can and will simply say "Thanks, but no thanks".

You know what the slippery slope is ? A logical fallacy, that's what.
The GOG team might as well say "just 3 bucks less" - a similar kind of a slippery slope... and just as likely.
The truth is quite simple - the negotiations WILL take place, regardless of the pricing options available. The GOG team will, most likely, still get the best price they can. The only significant thing that will change will be the three types of situations now:
1* "OK, there you go" / "Damn - we can't sell it cheaper than $5.99, 'cause that's the lowest price-point"
2* "$7. How does that sound ?" "That not really an option at this point... How about $5.99 ?" "Nah, that's a bit too low." "Well - that leaves us with $9.99..."
3* "How about $9.99 ? It'll pay off !" "Sorry guys, come back when you can offer me something that can be split between all the parties involves."
Three types of situations where we ultimately get screwed because of the very thing you claim is saving us. IMO - five fixed options are better than two.
Even if you are right and it may hurt us is some cases - there will also be occasions, as outlined above, in which it might as well help us.

It doesn't mean they have to kowtow to the publisher... except that's exactly what the higher price point means. Just another concession.

You see it is a concession, I see it as a smart business move that will benefit both GOG and us in the end. Frankly, I think you are being far too cynical about this whole thing. Understandable, considering the history of the gaming industry and its pricing policies. However, if GOG has proven one thing to me in the 15 months I have been with the site: its that they are the exception to the rule in the gaming industry. It is a company with integrity and truly holds the customer in highest regard.

Look I'm not saying they'll suddenly hike up the prices to 50 bucks or anything. I'm just saying that when you start making concessions to publishers like this, to businesses, who unlike GOG, do not care about those gamers requesting ancient outdated games, you are at risk of undermining the very essence of GOG. I guess.
I really didn't make my point clear here. I'm quite tired. I'll write up something more coherent tomorrow.
3 bucks less for games? That's a slipper slope I could get behind.

You've hit the nail on the head here. It's this Kotick crap and the DRM nonsense that is really turning me cynical game-industry wise.
I know Gog is the exception. I don't want their well intentioned concessions to money grabbing businesses (yes, all business want as much money as possible but you can go overboard [kotick]) to ruin their... ethics, I guess.

I'd honestly, literally be willing to pay anything if it allowed me to play my favorite games DRM free, cheap or not, the fact that I can get these old games, legally is INVALUABLE.