<xpath expr="//span[@t-field='l.price_unit']" position="replace">

            <t t-set="value_split" t-value="'{:g}'.format(l.price_unit)"/>

            <t t-set="decimal_split" t-value="str(value_split).split('.')"/>

            <t t-set="add_separators" t-value="'{:,}'.format(int(decimal_split[0]))"/>

            <t t-set="result" t-value="add_separators.replace(',', '.')"/>

            <t t-if="len(decimal_split) > 1">

                <t t-set="final_result" t-value="','.join([result, decimal_split[1]])"/>

            </t>

            <t t-if="len(decimal_split) == 1">

                <t t-set="final_result" t-value="result"/>

            </t>

            <span t-esc="final_result"/>

        </xpath> 

found the answer