Whilst cost is a factor that couples consider when starting a family, it is not the sole factor.
The baby bonus is not a substantial amount in the first place, but I do not think that increasing the baby bonus would result in a higher birth rate. Having babies is not a simple matter of being 'reimbursed' for baby expenses alone!
If you scrutinise the statistics, you'd see that other races are not experiencing as drastic a fall in birth rates, compared to the Chinese.
Central to that is probably the fact that most young Chinese couples tend to put career before family. Since it's a common scenario for both parents to be working long hours in a stressful career, having a baby means yet another stressor in their lives. They may not necessarily have the support network to help them take care of the baby whilst they are at work and the wife might not necessarily be willing to give up her career to be a full-time mom. Besides, the couple might not be able to survive on a single-income alone.
On top of that, the fact that there is a desire to give their child(ren) 'the best' that they can afford. This means that they might not want to have too many children as it would then be much too expensive to give every kid 'the best'.
Next, look at our work environment. How many employers are enlightened enough to provide 'Family Leave' for their employees? It has also been years since the idea of Paternity Leave was first mooted in the papers... how many firms here have ACTUALLY implemented that?
And have we not heard about employers who discriminate against pregnant employees?
In a country where the majority of women in the workforce are also working moms, employers need to offer more to provide a more family-friendly environment. It is not compulsory, since the raison d'etre of corporations is to ensure profitability, but it will certainly motivate their employees to know that the company they are working for, cares.
It is a social responsibility that most companies here have yet to pick up. Enlightenment remains elusive.
In the meantime, instead of dangling a carrot in front of the donkey, the govt seems to be missing the point altogether by dangling unattractive and inappropriate bittergourds on their stick.