A few main factors that usually determine the bulk of the reno quote price.
Every ID has their own way of calculating the costs for the above. Some bundle it up, some breakdown. It is recommended that you check out projects completed with pricing breakdown indicator for your house type here to get a more detailed picture about each component of the renovation works.
Example 4-room HDBS with pricing breakdown is available here: https://www.hometrust.sg/projects/latest/4-room-hdb/type--1/cost--breakdown
Hope it helps babe!