Would be nice to know what monitor is being used....
Budget is obviously an important factor, but as others are saying, buyers don't always know what their performance target costs. Certainly it's better to have a client with a generous budget than one that expects to get more than their budget allows. However, you don't always have to spend the whole budget, especially if the performance/aesthetic targets make it unnecessary.
Budgeted money is great, but it's not like the money you don't spend just vanishes. The client can use that money for other things in their life, even if they set it aside for a PC purchase. An extra $500 to spend elsewhere in life isn't insignificant. When you're working with a generous budget, you just need to be careful not to "cheap out" on something that the buyer may later regret, especially since they had the money available to get good quality stuff. That being said, I haven't seen any glaring quality sacrifices being suggested here.
On the flip side, you also need to make sure you can justify "upsells" so the client doesn't get smart later on (either on their own, or via external factors) and regret spending extra for something that they can't justify (spending >>> for RAM speed that gives near-zero performance gain, spending >>> money on an AIO that barely/doesn't reduce CPU temps compared to air/alternative, spending >>> on a mobo that doesn't increase performance or add features, etc etc)
That's why I like to give "baseline" builds (again, something befitting the original budget and performance target), then present the client with optional upgrades and have the conversation for each upgrade. Educate the client and let them make the choice, then your hands are clean.
Ultimately, PC builds have plenty of "grey area" for variety. There isn't necessarily one right/perfect answer, especially with constantly fluctuating component prices.