alt Hacker Newsyeah, so $500 spread https://www.microcenter.com/product/699008/nvidia-dgx-spark is what the current price appears to be.
The differences are basically, sparks require ARM and sparks allow interconnects; so if you do have dreams of electric sheep to chain them together, you're not gonna get the AMD halo units.
But if you just want to putz around with a dev machine and do other things, not sure you'd want a spark.
They had it on sale last week for $3999, it will likely happen again. Also if you are willing to buy ASUS/Acer/MSI you can get them cheaper, in the same range as well. Those units are identical (mainboard/ram/chipset/connectivity), they only tend to differ in SSD being offered.