Cost depends on a lot factors such as age, existing conditions etc. The total cost for me was around 3200 which includes both my parents plus I took the enhanced package.
Update: Jan 18, 2024
The eligibility status for the parents was updated to ‘Completed’. As of now, there has been no medical request, and the background check is still in progress.
Timeline for my parents-
Application Submitted via IRCC portal: Dec 19, 2023
Pre-medical: No upfront medicals done
Biometrics: From previous visitor visa application
Still waiting for medical examination request.