Pink is right. Let's follow a simple example. The higher is the resolution, the higher the textures are. The guy making the textures will have to work more ad harder to give the game higher quality textures. He'll work more time, more time means normally getting more payed.
Now imagine that with all aspects of a game in the making...
Bumping resolution makes games more expensive, it's just natural.

@BG

Yeah but it's not just the graphic assets themselves that need to be made tho. You can't just go and change a few lines of code and hope the game performs well at native 4k with Ultra settings. You have to find a resolution and effects that makes the game still perform well, then it might need optimising in all the right places for these settings, and then it needs to be thoroughly tested.

This isn't something that you do in a few minutes, this is lots of time spent by more than one person...

@jason

It's always funny that the people that really do not know a single little thing are only able to hurl insults!

@pink, that has more to do with optimization than creating the base game.

@PiNkFaIrYbOi: >"Yes that is why so many great ports go to pc."

Huh? The issues with ports are almost always in the form of bugs, not graphical problems.

@BG11579: > "The higher is the resolution, the higher the textures are. The guy making the textures will have to work more ad harder to give the game higher quality textures."

Doesn't work that way. Is it harder for you to create a 4K file in photoshop vs a 720p one? The answer is nope. Devs create high quality assets and downscale them as needed. They may or may not use that resolution to implement more details, but frankly at this level it's a diminishing return. Bottom line is a high resolution texture doesn't have to take even a moment more than a lower res one.

Aenea!

It's not an insult that you don't know anything, it's a fact.

Still cost money to implement that stuff in the game. Each version has to be tested. Testing can be costly.

@others refuting element

Most objects and textures in games nowadays are created at a rather high level that wouldn't be possible to use in the game themselves on any platform. They are then downgraded to a point where they can be used, and often times, you may not see much difference in some things if it is significantly reduced due to how textures work, and the ways that polygon objects are rendered on screen using various effects(or tricks) to make them appear to be a higher quality than they really are.

This is typical, and actually is a lot easier than making a lower quality model and adding to it, as you basically have to do twice the optimization on an object as you increase it's quality or polygon count. Going from high to low though, there is less, to no optimization in the higher quality versions of the same thing.

This however, does not mean that it's as simple as just using higher quality objects, as the objects or textures in question will still be made at a much higher quality than what any GPU could handle today. As it's reduced, each version will be moved lower to accomadate what would be possible on various versions of the game.

For the most part, on PC, there will only be a few versions of different quality levels of any individual object or texture....not unlike a Level of Detail model. The sliders which allow for a seemingly exhaustive selection of options only applies different effects to those things. This wouldn't be a good way to handle console games, as it reduces the efficiency of the build, and would lead to wasted resources for things that wouldn't be used.

Because of this, it's better to tailor make individual models, thus making ElementX's assertion that it's as simple as throwing in a different model even less relevant, because console programming really doesn't work like that, and each build will require it's own testing to fix problems that would arise due to the use of different models.

I wouldn't say it costs nothing, as fine tuning a down grade can be a time consuming process to make it look just right. The biggest reason for starting high is that it's much easier to scale down than up. On top of that, any future enhancements can be done much quicker as new hardware becomes available.

In this case, I'd imagine that the higher quality may be done first, then downgraded to X1X or PS4P, then again for the base consoles. But each part does require that time and effort to make it look good. Maybe less time on the mid-gens due to less work needing to be done, and a lot of things can be done quickly. Tweaking object models can be the most difficult part, and then making sure the textures still look good on those downgraded models can also cause tweaking in the textures.

It's a common task, and nothing new even for the stock consoles.

The bigger the game though, the more work that needs to be done, then the testing to make sure it all works, and the continuous cycle of tweaking everything to make it work good. I see less time being spent on the mid-gens because of the lower install base, and the penchant to just brute force marginal gains because it's the easy thing to do.