Don't show product price in some categories.

How do I get in some categories on the product page does not display the price of goods?
But the rest leave as it is.

No, I can not remove them. I need them for further calculations.

How should look this condition? To weed out some of the categories.
Can you give me an example code please.

Thanks, I'll try.
By the way, I actually even easier to select products by id, that price will not be displayed.
(I have only few of them, but in different categories)
Later write the result.

I figured out how to not display the price of the product by ID.
But there was the following complexity...
The product have characteristics and it appears that each characteristic - a product with a different ID.
Besides, as I understand it, the characteristics do not have bindings to product category?

For now, I made ​​sure that did not display the price of all products that have the characteristics, but this is not a complete solution for me because may be other products with the characteristics, in which will need to display the price

How to remove a price only for those products which do I need? How best to do this?

Thanks, it helps.
I've blocked "price-listing" for my 3 products by main product ID.