Hi David.
While I suppose it could be done, ClassiPress is not designed for price comparison, and would require heavy modifications to do what you want.
This would not be officially supported.
thanks for your answer.
I understand that this would not be officially supported. But the main question how difficult is to adapt this script for categorized products listing and filtering?
The advanced search feature is designed for filtering by custom fields out of the box. So... with a bit of child theme know-how, it shouldn't be that difficult to take it up a notch or two.