> every ISP would be giving every customer a block of addresses, both commercial and residential customers.

or more likely, you would still receive only handful of addresses and would have needed to be far more considerate what you connect to your network, thus restricting the use of IP significantly. Stuff like IPX and AppleNet etc would have probably then been more popular. The situation might have been more like what we had with POTS phones; residential houses generally had only one phone number for the whole house and you just had to share the line between all the family members etc.

They worked around this with IPv6 by the fact that SLAAC exists and some devices insist on always using it. Your ISP has to give you at least 64 bits of address space or else some phones won't work on your network. And even if they only give you the bare minimum of 64 bits, you can subdivide it further without SLAAC if you know what you're doing.

Furthermore, the use of privacy addresses obfuscates how many devices you have.

The phone company would have been happy to sell you more phone lines. I knew people who had some.

But you're right that as dumb as it is, it's likely that ISPs would have charged per "device" (ie per IP address).

Before 1983 in the US, you could only rent a phone, not own one (at least not officially) and the phone company would charge a rental fee based on how many phones you had rented from them. Then, when people could buy their own phones, they still charged you per phone that you had connected! You could lie, but they charged you.

Like I said, I have mixed feelings about NATs, but you're right that the companies would have taken advantage of customers.