Nah. Difference between SIM and the local uni is research output. Research output determines international standing which then boosts employability of undergrads.
Contrary to popular belief, universities are not meant for teaching smelly undergrads alone. It's about acquiring knowledge in general. So a university needs lots of funds for this endeavour.
Furthermore, SIM's courses is mostly biz and social science. All the school needs are classrooms and chairs. NTU/NUS has huge engineering/science departments. Most of the equipment can cost millions of dollars. So even if a biz/humanities student pays the same as an engineering/science student, it's obvious that more funds actually go towards the science/engin since they need it more.
Also, NUS/NTU can command that sort of price. They have the rep and track-record. Even if they increase fees, no one would choose SIM over them.