writes "It is said there are ISPs with hundreds of thousands of users behind NAT. I used to assume this was because they had to pay a small but non-negligible fee for IPv4 addresses. But someone pointed out to me that you get all the addresses you want for a low yearly fee. The difference between the fee for small ISPs and the biggest ISPs is only about 3000 Euros. That seems negligible for a large ISP, even one in a poor country with fierce competition, especially when you factor in the cost of NAT equipment and management.
So the question is: If they can get IP addresses now for nearly free, why don’t they? If they don’t want the IP addresses, are they even going to care when IPv4 addresses run out? Is the incentive to give customers IPv6 addresses ever going to overcome whatever disincentive there is now to give customers IPv4 addresses? Will we have to wait multiple decades before they decide to enable IPv6?"Link to Original Source