<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>
        <record id="product_normal_cump_form_view" model="ir.ui.view">
            <field name="name">product.normal.form</field>
            <field name="model">product.product</field>
            <field name="inherit_id" ref="product.product_normal_form_view"/>
            <field name="arch" type="xml">
                <group name="general" position="inside">
                    <!--<label for="purchase_price"/>-->
                    <field name="purchase_price"/>
                </group>
            </field>
        </record>
        
        <record id="product_normal_cump_tree_view" model="ir.ui.view">
            <field name="name">product.normal.tree</field>
            <field name="model">product.product</field>
            <field name="inherit_id" ref="product.product_product_tree_view"/>
            <field name="arch" type="xml">
                <field name="state" position="before">
                    <field name="standard_price"/>
                </field>
            </field>
        </record>
    </data>
</openerp>
<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>
        <record id="product_normal_cump_form_view" model="ir.ui.view">
            <field name="name">product.normal.form</field>
            <field name="model">product.product</field>
            <field name="inherit_id" ref="product.product_normal_form_view"/>
            <field name="arch" type="xml">
                <group name="general" position="inside">
                    <!--<label for="purchase_price"/>-->
                    <field name="purchase_price"/>
                </group>
            </field>
        </record>
        
        <record id="product_normal_cump_tree_view" model="ir.ui.view">
            <field name="name">product.normal.tree</field>
            <field name="model">product.product</field>
            <field name="inherit_id" ref="product.product_product_tree_view"/>
            <field name="arch" type="xml">
                <field name="state" position="before">
                    <field name="standard_price" sum="Cost"/>
                </field>
            </field>
        </record>
    </data>
</openerp>
Add sum on tree view
Add sum on tree view