Our local friends do not understand why the hell we spend a small fortune on car seats for our 5 yr old twins (we bought the Recaro Start). They even find us crazy if I tell them I can not give them a ride as there is an airbag in the front passenger seat which can not be switched off. Their reply, my child can sit on their lap.
When we shopped for a car, the car dealers find us crazy that we were looking at the back seat as we needed to fit the two car seats and guests.
The point is, why risk injury on your child (and I have seen the aftermath of kids in car accidents when I was working as an ER physician) if you could avoid it at such a small cost. You will regret it for life if something would happen to your kids, because of saving some pennies. Especially here in Singapore, no matter have a safe driver youa re, your fellow road users are the ones exposing you to an increased risk,
The worst thing I have seen was a local family using the Safety First table booster seat (the colourfull one with attached tray), strapped on the back seats using ropes and the 3-point seat belt. We were parked next to them and they had a look at ours. When I commented on the dangers, their relpy: this one only SGD 30. Also can. Is booster seat. Never mind it is not an appropriate car sea. Penny wise pund foolish.