I think one of the reasons for the increase in price is that more people are requesting for it. But another reason which I am certain about is the naira devaluation that is causing rise in the costs of goods and services.
Making laws and policies in Nigeria has never been the problem, it's enforcing them that's the issue. I think international passports will still be expensive because the people who are supposed to enforce the new policy are the people it affects negatively.
The people at the immigration office make money from people who want to get international passports, and this new format will stop them from ripping people off so it won't work.
Like you said, the rate at which people request a passport is high because a lot of people want to leave the country and this is an opportunity for the immigration officers that they must exploit no matter what laws are put in place.