Well.. all the information used in the page is contained in the source of the page (so it's obviously just passed through by the PHP or whatever server side script they use) in a <script> tag.
I'm not sure how easy or difficult it would be for you to access, if you can use javascript at all then it should be easy but from what you've said that's not possible. You might just be able to lift it and parse it as JSON (it does seem to be legitimate JSON) and then access the variables within that way...

If you want to see what information is there you can just type gogData in the console and look through it (to see if it's any use before making any effort to access it).
The important bits being;
gameProductData
which contains a series variable with various information
The price variable within series contains the original price, the discount (in percentage and amount) and the total bundle price with the discount.
There's also a products array with info on all items in the bundle (including their prices as part of the bundle)

It has data for both the normal series discounted and the current Enhanced Edition Bundle (though it seems to only include the two Baldur's Gate EE games and not Icewind Dale, though it has the correct 60% discount), so it seems to cover both scenarios but I'd have to check when another bundle discount (the Deponia one works, but as it is also a series I'm not sure it's ideal) is on to make sure...
I seem to remember we discussed the issue of finding bundle sale prices was actually that the promo urls were the only easy place to get them and those weren't logical or predicable in anyway...

I'll keep looking for anything else that might be useful.

Thanks. I'll look at it tonight.

But from the numbers you mention it doesn't sound correct. The bundle discount for the BGEE, BG2EE and IWDEE (when bundled together with BG, BG2 and IWD) is 85%, not 60%.

Yeah, I was typing while looking, I'm not sure it's any use for the non standard series bundle discounts (the sales ones like the EE one), but I'll keep poking about.

Pre-post edit: I only get 60%... are you sure you're not counting the discount for owning the originals?
I get 85% off IWDEE because I own that, but I don't have either of the BG games so the whole bundle is only listed as 60% off for me..

I do count the discount for owning the originals. But the way GOG works is that if you buy the originals and the EEs in one go, you get the 85% applied.You don't need to separate it into two purchases.

So, if you have a cart containing BGEE + BG2EE + IWDEE + BG + BG2 + IWD, you should get 85% off for the first three (which is the bundle discount I am looking for). I didn't test this specifically for this combination because the full cart scheme stopped working before this sale came on, but that's how it was on previous sales.

Ah, I missed the bit about buying the originals too.
No it definitely isn't picking up that.. and as that bundle and discount isn't even in the promo page I'm not sure there is an way to pick something like that up other than by doing what you were already doing..
I'll have another poke about though, just in case. Perhaps looking at the actual cart and how the discounts work there might help...

Yes. That's the problem. The info appears to be calculated server-side on the cart (which is why I get server errors). And while the everyday bundle discounts can be obtained from the game page (even when they are not in effect because there is a sale bundle discount that obviates them, but that's another story...), the sale bundle discounts are the tricky ones.

The sale bundles are indeed tricky... the specific case here (of the EE games being cheaper when you own the originals) causes weird behaviour. The actual javascript has no information on the 85% discount, only the normal 60% one, despite the 85% one showing.
But, if I go into the Network Tab there's an AJAX call to userData.json, which contains a list of ids and personalised prices which is where the discount appears.
If you just visit userData.json it won't give you this as you need to send a data object with it containing product and series ids to fetch the personalised data for.

Unfortunately, I'm not sure how useful that is to you or whether it's even something you could do anything with (if you made the call with a list of all the catalogue ids you'd presumably get a list with all of the personalised discounts back, but I don't know whether that will give you these discounts as presumably the account sending the query needs to own the base games, or have them in a basket)

It might be worth playing around with too, if it's not something you were already aware of / using.

Yeah, I think that's the best option. I've played around a bit with the userData.json link but I can't get it to actually return anything at all.. so I doubt it will be any use.
It seems adding the games to the cart is the only reliable way to find the bundle discounts, which is somewhat annoying considering GoG doesn't seem to like having too much in the cart at once.

This is probably a stupid, thought, but perhaps there's a way to somehow group games in order to have smaller carts?

One thing that is surely lost is that MaGog used to tell me how much the entire full cart cost, which was a nice private feature. Last time it still ran it was somewhere between $17K and $18K.

Heh, I have to say I made a quick script for my own private use to see how much my library was worth.

How are you adding games to the cart? Individually or in groups?
You can add multiple games at once or add by series Ids too (if you didn't already know that), if perhaps less calls to add to cart might stop it crashing...
Though that being said, I've tried to add the whole catalogue in one go and it just does nothing (no error though) but that could be because the list of IDs I was using was pulled from my legacy urls stuff and probably contains IDs that are no longer relevant which might stop it working.

I have an alt account to which MaGog once added all the games, then whenever a game is released she just adds that one. Now I'll need to determine which games to remove.

Ah, so the account is just permanently in a state of having all the games in the cart?

Edit: When exactly did it stop working?

Yes.

It worked well until late February. Then I began seeing intermittent failures. So I added retries (if server error, wait 30 seconds, then try again, give up after 20 failed attempts). This worked until a couple of weeks ago. Since then fails constantly.

GOG is aware of this. Actually one of the first things they did was empty that account's cart. MaGog of course filled it back again immediately. From what I informally heard they are not going to do much to fix it.