I don’t get it.

Amazon will now sell businesses virtual PCs for $35 per month. I’m trying to figure out how this makes sense.

Let’s run the numbers. You can buy a pretty decent desktop computer … from Amazon, to take one variable out of the comparison … for $400. Plus a monitor, keyboard and mouse, but they’re the same either way — a wash.

For the Amazon offering, unless you’re planning to run it directly in your frontal lobes you’ll need a cloud client to run it on. Typical cloud clients run around $350.

Imagine you expect the desktop PC to last 3 years … a typical rotation … but because you’re using a cloud-based PC you expect your cloud client device to last twice as long. That’s probably too generous, but I’m a generous guy.

The raw numbers say that over six years you’ll spend $800 for a traditional PC. For the Amazon alternative you’ll spend $350 + 12*6*$35 = $2,870.

Presumably, what you get for the additional $2,000 and change … $333 per year … is …

I don’t get it. Because you’ll still have to handle software installations, user support, and so on. The big benefit is that if a cloud client dies, there’s no disruption when you replace it. (And, by the way: Dear Microsoft … this is 2013 and it’s still an awesome pain to migrate from one PC to another. Why haven’t you fixed this yet? Love, Bob)

Probably, this is the wrong comparison. What we should be comparing Amazon Workspaces to is running your own VDI infrastructure. It’s a much more plausible comparison, because without Amazon you need to server capacity to run the virtual desktops, and storage capacity for user data.

Enter a nice piece written by Network Computing’s Art Wittmann earlier this year (“Calculating the True Cost of VDI,” 4/15/2013). Wittmann’s bottom line comes to $900 to $1,000 to provision a cloud-client system. The picture is complex enough that I’m not going to try to put a side-by-side comparison together.

Building a side-by-side comparison is complicated by quite a few little details, like how many times you’d replace the data center hardware over the six-year span we’ve allowed for VDI desktops (if it’s every three years add $320 per desktop for this, spent in year 4 of the cycle), and whether you or Amazon will upgrade the desktop OS, and if it’s Amazon whether the upgrade license is at no additional charge.

If you’re running low on space or AC, factor that in too.

Oh, one more quibbling little detail: If it’s your server, your local users get to operate at wire speeds. If you use Amazon’s service they’ll share Internet bandwidth. Yes, VDI is pretty efficient in its bandwidth use. You still need to determine whether you’d need to beef up your network.

Or add to it, because now that everyone is completely dependent on the Internet connection, you’ll need two, from two different ISPs, connecting to two different points-of-presence at opposite sides of your building. You should have this already, of course, and if you don’t, stop reading right now and make the proper arrangements.

I’m far too lazy to perform the detailed analysis, although if you’d like to put one together and send it my way I’d be happy to share it with the rest of the KJR community.

My guess is that managing your own VDI will win, but not by a lot.

But what this really points out is that after all these years of VDI being touted as the just-makes-sense alternative to putting real PCs in front of employees, the raw economics still favor the real PC.

VDI’s “value proposition” (if you aren’t an initiate: “Why you might want to buy it”) has always been the same. It isn’t hard cash. It’s headache reduction.

But reducing IT’s headaches doesn’t improve revenue, costs, or risks.

It’s long past time for a hard-edged look at the trade-offs between using VDI-provisioned desktops and real PCs. Not just how the costs compare … I trust regular KJR readers don’t need me to explain why total cost of ownership is such a useless metric yet again … but how they compare with respect to the business benefits they enable as well.

But this will probably prove impossible, because much of the benefit of real PCs comes from “shadow IT.”

It’s something most IT departments still try to stamp out, because IT only sees the headaches it causes. Its benefits are, by definition, hidden in the shadows where they’re devilishly hard to dig out.