The real sinker here is that for business use you will have to buy the retail version of Windows (if you want to do things the legal way). This tacks on at least an extra $100 per machine; however, if you already have the OS software separately, then this is not an issue.
Compare:
20 copies of Windows 7 Professional (OEM License) @ $134.99/ea <-- Can only be sold with a new machine to an "End User"
20 copies of Windows 7 Professional (Retail) @ $265.99/ea
(this includes volume savings)
Another option which MAY work (you'll have to check the fine print): it might be possible to just get an OEM System Builder License from Microsoft, start your own computer making business (wouldn't be too hard to do), and then sell the computers to your company. See this website for more details from Microsoft (
http://oem.microsoft.com/script/contentpage.aspx?PageID=552816). This arrangement should be legal (you are a sole proprietor selling goods to another corporation, who qualifies as the end user), and it also has the advantage of letting you buy Office at a heavily discounted price (so long as you bundle it with a newly created machine). However, this opens up a whole can of worms with the IRS too (as you now own your own business, and they can tax your "income"). It might also be possible to register your business to purchase Direct OEM licenses from Microsoft (which would circumvent all the rest of the hullabaloo). At any rate, check with your company's legal department and read through the fine print with Microsoft if you decide to attempt this.
Still, let's see what we can do even if we're handicapped by the retail version of Windows 7:
Here's the same machine as Dell quoted:
Mobo:
MSI G31TM-P21 $44.99
CPU:
Intel Core 2 Duo E7500 Wolfdale 2.93GHz $119.99
RAM:
Mushkin Enhanced Silverline 2GB DDR2 800 $47.99
HDD:
Western Digital Caviar Blue WD800JD 80GB $35.99
Optical Drive:
SAMSUNG Black 22X DVD+R $30.99
Case & PSU:
Rosewill RS-M136-BK $29.99
Keyboard & Mouse:
Logitech 967973-0403 $16.99
OS:
Microsoft Windows 7 Professional - Retail $265.99 @ Volume Prices
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Grand Total: $592.92 ($470.92 with OEM Windows 7)
You could also get a much better machine for just a little bit more:
Mobo:
MSI G31TM-P21 $44.99
CPU:
Intel Core 2 Duo E8500 Wolfdale 3.16GHz $189.99
RAM:
G.SKILL 4GB (2 x 2GB) DDR2 800 $89.99
HDD:
Western Digital Caviar Blue WD3200AAJS 320GB $47.99
Optical Drive:
SAMSUNG Black 22X DVD+R $30.99
Case & PSU:
Rosewill RS-M136-BK $29.99
Keyboard & Mouse:
Logitech 967973-0403 $16.99
OS:
Microsoft Windows 7 Professional - Retail $265.99 @ Volume Prices
------------------------------------------------------------------------------------
Grand Total: $716.92 ($594.92 with OEM Windows 7)
So, even with the Windows 7 handicap, we're still under Dell by decent margin (~$50 per machine). If you can reuse old cases, optical drives, and keyboards & mice, that shaves off an additional $77 per machine! Keep in mind too that Dell will charge you tax, NewEgg won't (except for state taxes); thus, you will save an additional $45 per machine (assuming 7% sales tax). If you can reuse to old components (cases & optical drives) and if you count sales tax, you will certainly be under by at least $150/machine. If you can work out a way to legally get the OEM license (or if you just don't care) you can save a heck of a lot more.