eiru_commision_product/views/product.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
  <data>
    <record model="ir.ui.view" id="commission_product_template">
      <field name="name">commission_product_template</field>
      <field name="model">product.template</field>
      <field name="inherit_id" ref="product.product_template_form_view"/>
      <field name="arch" type="xml">
        <xpath expr="//page[@string='Sales']" position="inside">
          <group name="comisiones" string="Comisiones">
            <field name="comision_vendedor"/>
          </group>
        </xpath>


     </field>
    </record>
  </data>
</openerp>