This article is from the Macintosh for sale FAQ, by Elliotte Rusty Harold firstname.lastname@example.org with numerous contributions by others.
At various times Apple repackages different models of LC's,
Classics and Quadra's with slightly different software and sells
them as Performa's through consumer outlets like Sears. With
one exception (the Performa 600) these have all been virtually
identical to one model or another of the Macs sold at authorized
dealers except for the bundled software. Most of the time the
regular model is cheaper than the equivalent Performa, especially
if you don't want the bundled software; but this isn't always true
so you should double-check the price of a Performa compared to the
model you want to buy. Finally most Performa dealers will sell Macs
over the phone to customers they've never met. So if you can't find
what you want locally, a Performa may be a reasonable choice.