My company didn't spend $5000 each on Mac Pros. That's ridiculous!
Maybe your company used off the shelf, stripped-down MPs, but I doubt that is the "average", any more than people buying a new car with no extras. (Though I'm that sort of car buyer, LOL.)
I'll use my MP purchase of the newly released early 2008 MP as an example of a typical user - I bought the unit wiith NO apple extras, and then built it up myself with the cheapest third party parts I could buy. (I'll round down to minimize total price).
Base Unit (2 x 2.8Ghz/ 2GB / 320 GB) - $2500 + Calf tax = $2700
Additional 8 GB of RAM (OWC) = $470
3 @ 1 TB Seagate HDD (newegg) = $930
Base unit + 8 GB RAM + 3 TB HDD = $4100
I still haven't added ANY monitors, or my graphics card upgrade ($300). In my case the one luxury I splurged on at this point was an expensive Eizo 24" monitor for color correction ($2000) paired with a cheap Dell 24" ($400). But anyone buying a 30" monitor would have also dropped a lot of cash, priobably $1500-2000 as well.
Note that any of these upgrades via the Apple store would have brought the price WAY up, esp with Apple RAM at the time.
So given that I tend to buy middle of the road stuff and upgrade later when prices are even cheaper, I doubt that the "average" new MP user spends much less than $5000 on a new system. While a few will run a stripped down, bare bones system, there are others who will max out the same unit (current price for 64GB of RAM at OWC is almost $3000).
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Edit - I should also add for people used to buying cheap consumer models that the MPs, as professional workstations, are still very good value, and comparably priced to workstations from other companies. My 2.5 year old processors still beat out the latest, fastest i7 consumer desktop processor in speed. The beauty of the MPs is that users can use third party solutions to fix other important bottlenecks in their systems to extend the usable life. A nice eSATA PCI card and external HDDs can add in additional massive RAIDS for 250 MB/sec access, etc.