See the demo.

        var distance = e.total.scalar;

        if(e.total.unit === 'mi'){
            distance *= e.sub_unit;

        } else if(e.total.unit === 'km'){
            distance *= 3280.84;

        } else if(e.total.unit === 'm'){
            distance *= 3.28084;
        }

        var cost_underground = 12.55,
            cost_above_ground = 17.89,
            html = [
                '<table>',
                ' <tr><td class="cost_label">Cost Above Ground:</td><td class="cost_value">${total_above_ground}</td></tr>',
                ' <tr><td class="cost_label">Cost Underground:</td><td class="cost_value">${total_underground}</td></tr>',
                '</table>'
            ].join(''),
            numberWithCommas = function(x) {
                return x.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ",");
            };

        var data = {
            total_above_ground: numberWithCommas(L.Util.formatNum(cost_above_ground * distance, 2)),
            total_underground: numberWithCommas(L.Util.formatNum(cost_underground * distance, 2))
        };

        if(e.rulerOn){
            var content = L.Util.template(html, data),
                popup = L.popup().setContent(content);

            e.total_label.bindPopup(popup, { offset: [45, 0] });
            e.total_label.openPopup();
        }
    }
});

map.addControl(new Core({
  unitSystem: 'imperial',
  color: '#FF0080',
  type: 'line'
}));</code>