RM 3.20-3.80 is consider ok price.

If RM 2.50 , few things need to be concern.

1)With this price, and his workmanship is good and reliable and honest.

Normally his job will be fully booked for 3-5months. If with this price also very free to take the job anytimes....Must be something "heehee

2)How much space/gap that he use to do the framing structure?

It can be 2ft(Normal RM 3.0-3.5. For 1600sqft, can go to 3.0-3.1) to 4ft(the worst I had seen) of course the wider the cost is lesser and the strength of the plaster ceiling is weak .

*just my 2 cents, it doesn't represent to the market sounds