Time it takes to upgrade?

Looking to hire someone to upgrade our version to 1.5. For someone that knows there stuff about how long should it take?
One person is quoting 600.00 for the job at that seems high?

It depends on how much customization you've got on your site, especially core-file overwrites and plugins that affect the admin area.

If I were going to request a quote, I'd have a zipped version of my store's files (with my admin folder renamed to admin and minus the /includes/configure.php and /admin/includes/configure.php). That would give the person giving the quote a chance to see what's different between your store and the "core" zen-cart distribution ... giving them a good feeling as to the work required.