How much should a good 3D icon cost?

[Matthew James]

I'm in the planning and design stage for my first Mac OS X application
and have been thinking about the icon for my application.  I know very
well what I'm looking for, but am wondering what I should expect to be
charged for a nice 3D icon.  My expectations of the designer are to
iterate through a few versions of the design until it's as I imagine
and then to produce a model that can be manipulated as seen fit for an
icon and marketing materials.  I assume that a designer would charge
first for the model and then for whatever subsequent manipulations of
that model I require.

Does anyone have any experience dealing with this sort of thing that
they can share?

Thanks!