it's not about economy. The reason ipv4 is uniquitous and ipv6, yet more than 10 years old, is not used universally, is not an economic one. Upgrading is a question of software, not hardware. So, why is it not used? Because in ipv4, one can ping every device in existence via brute force. It's only about 4.3 billion addresses. But, ipv6? Yeah, that's quadrillions of quadrillions--an intractable amount of devices to ping. You are not wrong that there are trade-offs, but it's not enough of a reason to keep the internet held back using such antiquated tech.