A random thought on passport fees

I wonder, if the fee for a passport with 2-year validity is RM100, then why does the immigration department is charging RM300 for a passport with 5-year validity? If it were up to me, I'd charge RM200. This will create an incentive for people to select the 5-year option. Then, people would renew their passports every 5 years rather than every 2 years. Of course, this applies to people who travels abroad all the time. People who don't travel abroad so often would probably still choose the 2-year validity option. Still, let's say the two groups are evenly split. By applying for the 5-year validity option, half the group would apply 67% less number of times, hence half of that is 33%. This roughly means that the passport-processing division can reduce their resources by 33%. Could this cost-saving be more than the additional revenue of charging more (for the 5-year validity passport)? The equivalent reduction in revenue is only about 16% (50% of 300-200/300). Of course there's still be people who wouldn't mind paying extra to avoid going to renew their passport more often. But could there be other reasons, perhaps the immigration department prefers if people have shorter validity passport than longer? National security, or whatever? Not that I can think of any.