I have create a securit group:

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <record id="show_cost_price" model="res.groups">
            <field name="name">show cost price</field>
    </record>
</openerp>

And a view:

<record model="ir.ui.view" id="show_cost_price_form_product_template">
        <field name="name">show_cost_price_form_product_template</field>
        <field name="model">product.template</field>
        <field name="inherit_id" ref="product.product_template_only_form_view"/>
        <field name="arch" type="xml">			
            <xpath expr="//label[@for='standard_price']" position="attributes">
<attribute name="groups">hide_cost.show_cost_price"</attribute>
            </xpath>
        </field>
    </record>

Odoo hide the label for all users ignoring the security group.