Hi,

1- By using the following code, you can make the cost field read-only for all users

<record id="product_template_form_view" model="ir.ui.view">

        <field name="name">product.template.view.form.inherit</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="//field[@name='standard_price']" position="attributes">

                <attribute name="readonly">1</attribute>

            </xpath>

        </field>

</record>

2- By using the studio.

Or by adding the readonly attribute in the product view, you can achieve this.

Hope it helps