Microcenter has them marked at $4500 right now (that's with the 4TB SSD) [1]. I suspect it comes down to what you're using it for; if you're looking for a general purpose computer that's also solid at AI, the AMD machine is better. But if you want the best possible AI machine at below $5k... actually you should probably just buy an RTX 3090 or 5090. But if the 128gb of memory is critical, then yeah DGX Spark is it.

[1] https://www.microcenter.com/product/699008/nvidia-dgx-spark