“Car make” is custom field which is shown only in “Transport” -> “Cars” and one other category in transport. It is not shown in property or job categories. You can define which custom field used in each category and subcategories. Price is also custom field as well. So you can have categories without price for example job listings. And have salary field for job listings instead of price.
Classibase is fully customizable in terms of custom fields and you can define them by category and location.
See for example property listing, there is no car make in property category. http://classibase.com/demo/item/semi-detached-house-76.html
Also check tutorial regarding using custom fields in Classibse classifieds script. http://classibase.com/how-to-add-custom-field-to-classifieds-website/