To have category specific pricing feature you must have the Enterprise Pricing addon installed and enabled in the ADDONS > MANAGE ADDONS admin tool.
This feature is only available in a fee-based price plan.
You do not set category specific price plans. You set category specific pricing within a specific price plan. That is an important distinction. You will not be able to create a price plan and assign it to a category. You will go into the "category specific pricing" section of a fee-based price plan and set category specific pricing for specific categories. Any categories you don't set category specific pricing for or their parent categories do not have category specific pricing will default to use the site wide pricing for that price plan within the COST SPECIFICS admin tool.
Highlights of the category specific pricing feature:
Items you can charge for on a category by category basis:
This feature is managed within a fee-based price plans CATEGORY SPECIFIC PRICING admin tool:
PRICING > PRICE PLANS HOME > [EDIT] (next to price plan to change) > CATEGORY SPECIFIC PRICING
On that next admin tool page you'll navigate to the category you want to set category specific pricing for and click "add price plan". Once you've saved that category specific pricing you can always return to the same admin tool and click "edit" to edit it.
Any category that has "click to add" next to it does not have category specific pricing attached to that category specifically but could be affected by a parent category's pricing if it has any attached to it.
The following screenshot should explain the process in the admin tool.
You click:
PRICING > PRICE PLANS HOME > [EDIT] (next to the price plan you want to change)
You then click CATEGORY SPECIFIC PRICING
Things bring you to admin tool where you can