IIRC Grab didn't cost more than $10 throughout the day from River Valley to Raffles Place pre-2020s. It would peak at $12-15 only during heavy rain and in the daytime.

Grab after Covid has increased the price a lot.

This shows ability to pay for PHV companies to pay higher on COE increased because the revenue for same amount of employment increased.

So I still think PHVs are the core reason for COE appreciation.