You sure you downloaded the correct version? I am serious. There are several such games and one of them currently doing a bundle sale is having a price tiered version and a free version. Also I am not sure how this is calculated, since at least one of those games acutally has three tiers. A free version, a full version and a deluxe version.
If you bought what I think you bought, you bought 3 games at the 8 $ tier. In sum 24 $. The bundle price is reduced by 20% making it the 20 $ the bundle costs.
I wish there were more clarification how bundles work in regard to individually priced files. Some people might think it applies the bundle price to all items in the bundle. But I have doubts this is so. If you bundle 10 items, you would give a discount of 90% just by having them in the bundle.
Also, itch absolutely NEEDS to implement the ability to increase the donation level. This is ridiculous! Unless I am mistaken, you were in error what you would get because of the unseen consequences of the bundling/individual donation level after purchase. And if you were to correct the mistake, you can't, since you cannot just add 12 $ to your tier. And how discounts affect the calculation is also rather unclear to me. Ideally you would pay 12 * 0.8, because the games currently have 20% discount. But as I said, you cannot do this, as you would only buy the game a second time and not increase your donation level.
(For the record, the deluxe price for all three games would have been 60 $)
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Yeah, my math is off above, sue me. Bundle prices and individually price files do not go well and there is lots of assumptions made. I now think the dev set the indivudul games on "sale" by 20%, whatever that means for a free game with donations, and additionally made a bundle that might distribute the bundle price equally to those projects, giving each project a donation level of 19.99/3/0.8 = 8.33, putting buyers above the 7.99 threshold of the games.
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And yesss, bundles that offer no bundle discount are possible and quite nonsensical in many cases. It bundles the payment and reduces fees, of course. Unless it says something like Each item 10% off! or buy everything for $18.00! Regularly $20.00 Save 9%!, the bundle itself has no discount! Wrong again. It just means the bundle calculates the price for you, it is still the sum of the individual projects. Searching for a bundle that has a bundle discount now.
Each item 50% off! or buy everything for $9.99! Regularly $22.98 Save 56%! That one. The "save" value after the bundle is bigger than the individual discount, those bundles give bundle discount. And just look at the example above, the rounding made the individual 10% to a 9% bundle discount.
I'd say there are some serious issues with the whole bundle and sales labels and pricing options that projects can have. There is something wrong, if you have to contemplate and think and think again and again, how something is priced and what you actually get for your payment and what the actual discount was.