i found following in line no 42

 <field name="company_id" groups="base.group_multi_company" options="{'no_create': True}"/>

so where add "invisible="1"

Activate Debug mode and add invisible="1" or  invisible="True" for cost price field

i don't understand what you really need ?? 
if you want just hide it you can make it invisible 

#wih admin account

1 - open developer mode
2 - goto settings>technical view>user interface>views 
3 - search for <product.template.common.form>

4 - click edit and search for field name="list_price" < you can search in browser by click ctrl+F

5 - add invisible="1" to this line and save 

note : be sure that invisible attribute is seperated from both side with blank space to work write and don't damaged your view.

or if you need to deactivate the function behinde the scene it will depend of a lot such as your coasting method if any transactiondone for the products or not and so on .