Earlier quoted context omitted.
They can do it, but that gonna need to be different SKU not Mac Studio. Otherwise news will be full of discussions about Apple price hike from $8000 to $24,000 or who the hell knows $48,000. So yeah the only way I see them selling it is usual "call us" enterprise price tag. But since its not what Apple usually do its easier to sell 4x Mac Studio 256GB RAM boxes with interconnect for lets say $12,000 - $15,000 each.
I don't think it's needs 'call us' just a separate SKU, I mean if they called it Xserve Ultra and it was just a studio in a 1u format with dual PSUs and extra RAM, it would fly off the shelves.
And the reason people rarely use that for AI is that the enterprise GPUs from AMD and Nvidia are only moderately more expensive but are significantly faster because they use HBM instead of DDR5.