Seems like the Mac Pro is just incredibly overpriced because it provides a "box of slots" to upgrade it in the future, and of course you're not getting a display at all with it either. I used to love the older Mac Pro towers - but they were priced more "down to earth" so they were costly, but worth it for enthusiasts, power-users, professionals, etc. Now, the iMac Pro really fills that general space and this Mac Pro is as high-end as Apple could build the thing, seemingly to say "Told you we could do it!"
And some will purchase the new Mac Pro and immediately fill every slot. And, consider it a bargain, improving their workflow/productivity.