Well, if we're comparing apples to errr, pcs, then the equivalent to a $499 mini in specification (if not functionality!) is I'd guess barely $350-400. For $500 you'd get more ram, faster processor (although this is admittedly debateable), more hd space and a dvd burner...
It won't be as easy to use (in that lovely mac way), of course
(edit) or pretty!