By traffic it seems like "if only we didn't have these Rokus!" but it's a streaming device, it generates a lot of traffic compared to the other IPv4 only devices. Inevitably the long tail of devices is what's costing them extra (sounds like CG-NAT dual stack or 464xlat at the gateway) not just the Roku devices.
As someone who operates their own ASN with IPv6 because I like v6 so much the problem here was simply poor planning. Handing out Apple TV's to replace Roku devices isn't going to make the need for v4 services go away at these homes.
It may not reduce the need for IPv4, but it will reduce the need for costly CG-NAT devices and capacity for IPv4 when the streaming can happen over IPv6 which does not require the costly CG-NAT devices.
I may be mistaken on how many people this ISP is serving but for 300K they should have gotten pro serv, licensing, and hardware for ~100 million sessions, some of which now no longer need to go through the NAT64 hardware.
Hopefully they didn't buy through the same people that sold them the NAT64 hardware+software without CG-NAT built in though...
Wonder if ISPs will just let their CG-NAT get overloaded and if you want to send a v4 packet you just have to wait for your time slice on the hardware.
I've seen that. Too many connections, so the idle timeout is now ten seconds. And, as per usual middlebox NAT, no packets sent when closing an idle connection, and no response to packets sent on 'unknown' connections.
As someone who operates their own ASN with IPv6 because I like v6 so much the problem here was simply poor planning. Handing out Apple TV's to replace Roku devices isn't going to make the need for v4 services go away at these homes.