toinetoine1

Before the bridge the only way to get from HK to Macau/Zhuhai by land was 4+ hours. Now it's 20 mins. There other bridges being built further up the delta (like the Shenzhen-ZhongShan bridge which will cut a 2 hour drive to 10 mins).

You mentioned the cost-benefit. Making is easier for a region of 60 million people to get around obviously has a very high benefit.