1 The source of material unit price is different, and there will be some discrepancies.
There are some errors in the calculation of engineering quantity because of personal calculation habits, scale and drawing scale errors.
3 The understanding of drawings and quotas is different, and there will be some discrepancies when applying quota subheadings.
4 There is a certain discrepancy between the calculated amount of drawings and the actual construction amount.
The actual loss and fixed loss will also be different.
So the cost budget can't be accurate. Only reasonable.
People who say that the cost budget should be accurate are either laymen or so-called theorists.