As a large retail company we buy a lot of computers, yet we don't need much processing power on most of our desktops. Our solution to save a lot of money is to buy 3-year off-lease Dell Optiplex computers from CDI.
If you don't know CDI they are a major refurbisher of off-lease equipment based out of Ontario. Their stuff comes with a one-year warranty and is very clean, except for some cosmetic flaws. I've had the chance to tour their refurbishing plant and they run a pretty impressive operation there. The website I use to check their inventory is
http://www.warehousepoint.com.
CDI has been agreeable to working to fit our needs. They reserve a pool of 15 or so computers in their warehouse that they pre-image with our custom Windows 7 install, and they ship direct to whatever location we specify.
What you won't get with CDI is any type of next-day service plan, and I find that computer orders can take up to 10 days to arrive. Also, when buying off-lease equipment most components in the case are three years old, which for hard drives can be a problem depending on their history. Most of our failures are with hard drives, but I'm pretty sure we could have CDI put in new hard drives for us at an additional cost if we so choose.
The other thing we've learned is to research the models we're interested in, or to perhaps get a sample and give it a good look-over. All manufacturers put out lemons, but at least with 3 years in service design flaws that lead to early computer death are pretty well documented on the 'net.
Anyway, to supply computers to our stores we pay about $210 for a basic desktop (Dell Optiplex 755 with Core2Duo processor and 2 GB RAM, including Win7 license, keyboard, mouse), or around $320 for something with more oomph. CDI has a pretty tight relationship with Dell so that is mostly what they resell.
For a smaller shop like yours you could probably buy 3 computers for the price of 1 new Optiplex (if you don't need the latest) and have a ready-to-go spare, so long as you're able to do your own basic tech support. They do laptops as well and I've bought some off-lease and open-box models from them in the past. The off-lease models usually need to have their battery replaced before too long.
PM me if you'd like my CDI contact and phone number.