Could you please tell me about the relation between activities prices and activity cost ?

The name only. 😛

Without joke, It doesn't exist a direct link between planning activities and Activity price.

However, you can define a link between planning activities and a term.
The validated and planned amounts for linking activities are summarized in the term. (Information only)

Can be used to set amount of term.

Activity price:

Defines daily price for activities of a given activity type and a given project.
Used to calculate a billing amount for billing type: On produced work and On capped produced work.

Term:

Defines to generate an invoice, generally following a billing calendar.
Used with Fixed price projects.

You can link the activities that should be billed at this term.
A summary of activities is displayed for validated and planned amount and end date.
Validated and planned values play the role of reminder.
You can use these values to set real amount and date.

Cool 🙂 , Activity price sum labor, buildings, administration, depreciation of machines , etc .
So it is include Resource Cost which is added also in ProjeQtor ,
So should i add resource cost based only on his salary +benefits and exclude any other element like depreciation of his laptop for example .
While in the activity price is where i add cost of buildings, administration, depreciation of machines , etc
My question is ProjeQtor calculate cost based on Resource Cost+ Activity Price +Project Expense +Individual Expense ?

My question is ProjeQtor calculate cost based on Resource Cost+ Activity Price +Project Expense +Individual Expense ?

Activity price doesn't have links with project costs (Resource Cost + Project Expense + Individual Expense).

Activity price is just for billing.