When I was buying them in Austin a couple years back, I found they were about $600-$700 from used office furniture stores, though occasionally they'd show up on Craigslist for less. I bought the one I still have from the Arthur Andersen auction after the Enron scandal shut them down...got it for $385. I also got a truly awesome Keilhauer chair for $35 (list price ~$950, but everybody was after the Aerons, so the other chairs went for nothing, even though most were really nice chairs), which I also kept. Maybe Aerons come down in price in the past two years, or are cheaper here in the valley, I dunno.

But I agree, spending a few grand on every new employee for a nice working environment, the keyboard they like, a great chair, a good desk, a nice top of the line computer with dual monitors, is just sound business sense. The money spent will disappear into noise by the time you add their annual salary to their line on your expense report. And the work environment will last for years, just upgrade the computer every 18-24 months, and the monitors every 3 years, and you've got a fat and sassy employee that feels like you appreciate them (assuming you actually do appreciate them and treat them with respect in addition to giving them great tools with which to work). And the chair is the single most important part of that equation. I'd never ask anyone to sit 8 hours in a crappy chair.

Out of curiosity, where do you find them used?

craig's list, and if you are in SF or Oakland there are a number of furniture places that buy and sell them.