As the Old saying goes Dollar two-ninty-five (PS used by my late Uncle).
Joking aside, two factors:
1) Market for used laptops - small
2) Cost of equivalant Laptop Performance wise divided by 2, posibly divide by 3. A "New" i3 going for $400 is probably higher performance
If Dell consummer mode 3->4 years old would be a negaive, Positive if it is an enterprise model.
Best bet to get a realistic idea of value. Google it and go to ebay and see what they are going for - ie:
Dell D620 - $160 http://www.ebay.com/itm/DELL-Laptop-Notebook-Latitude-D620-14-1-1GB-Ram-1-6Ghz-CPU-Wifi-Ready-Purple-/170985942281#vi-content
Del 610 - $60 http://www.ebay.com/itm/DELL-LATITUDE-D610-LAPTOP-2GHz-2GB-60GB-/221183843482?pt=Laptops_Nov05
Personally I'd never sped over $100 for an older used laptop.
@ 06yfz450ridr - an iX, 3 -> 4 years ago, don't think so, Maybe a core daul, or a core 2 daul. at best an E6xxx
Added a referb Dell for $250 (better bet than buyng a used) : http://www.newegg.com/Product/Product.aspx?Item=N82E16834200598
Brand NEW SB i3's under $500: http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=100006740%204020%20600003986&IsNodeId=1&name=Intel%20Core%20i3