Pivot view Header and sub level (Product) Header Total value replace with custom formula. Example: Sub Level  Total value = (price * qty) = Product1 = Product 2 to product n

                 And Total Header value = (price * qty) product1 + (price * qty) product to product n

Please see the below image.

https://postimg.cc/xJWp54wC

Sub Level total customized read_group method override and formula price * qty applied.

But Pivot view header total not get expected output. please check the below code.

@api.model
def read_group(self, domain, fields, groupby, offset=0, limit=None, orderby=False, lazy=True):
    res = super(productreport, self).read_group(domain, fields, groupby, offset=offset, limit=limit, orderby=orderby, lazy=lazy)
    for line in res:
        if 'price_unit' in line and 'qty' in line and not 'id' in line:
            line['price_total'] = line['price_unit'] * line['qty']
    return res

Please let me know pivot header total value how to update customize formula.