Hi,
1.Once you have released the price for the period, you cannot change it. Even you can re cost the material for the period. Instead you can delete the current cost estimate by CKR1. Here you have to select the option "Current std cost esitmates" and remove the test run, execute it. This will delete the costing for the period.
2. As per your quantity structure the price has determined the system for the period as 119000. So, when you try to change it by MR21, system won't accept it.
Regards,
Mukthar