Do you have any example where leasing an ipv4 block from a NIC directly costs more than 5$ per IPv4 address per year?
China has very few IPv4 addresses per capita. Here in Hangzhou, China, I have to pay China Telecom 850 CNY per year just to get an IPv4 address. That's not a trivial amount of money for us. And among the three major telecom operators, only one even offers this service.
Counting the cost of creating the company so you can actually deal directly with a NIC?
Every. Single. Individual. End. User. Device. Should. Be. Addressable. Given that there are more such devices out there then there are IPv4 addresses to begin with, cost doesn't even come into it.
Yes. My ISP will rent me a single IPv4 address for $10 per month. Or I can use DHCP, where my IPv4 address can change at their whim.