Question for May Pen Roofing & Hardware Co Ltd

Dear Admin, I have a house in Sevens Estate, May Pen, and would like to change the design for two ceilings (Landing approx 20'x16', and Main Bedroom 15x13), from flat (and low) to a kind of vaulted (using tongue and grove wood).
Please advise if this is an expensive option, should I just paint the ceiling (decorative ply).
Regards
Ian M. Scarlett