IPv4s are about to be bought, held, portfoilo'ed, speculated, and rented/mortgaged/sold like real estate. Companies like IPXO are already doing it. The costs of public IPv4's are going to go up for no technical reason because a new distinct ownership layer is springing up between you and the ISP. You're going to start renting them or paying a holder for the right to use them (on top of your ISP to transport it) at some point. And you can continue to do that, or get IPv6's for free.
IPv4s have been bought and sold for years
https://auctions.ipv4.global/prior-sales
Prices have been going down in nonimal terms for years, let alone real terms. In terms of investment they're a terrible asset.
I'm a networking noob, but would it be possible to extend DNS/HTTPS so as to allow a URL to point to a port other than 443? Doing so would allow each IP address to serve multiple websites/computers making the pool of addresses at least thousands of times larger.
How does one get an IPv6 allocation for free? Or, do you mean the ULA space? Because the latter doesn't really count.
We own our own IPv4 and IPv6 ranges, which is nice. There already is a holder for the US: ARIN.net and I hear it's a pretty spendy annual fee for most orgs (we're legacy. we've had ours for decades)
Now all we need is for someone to make a crypto currency so you can fractionally own IPv4 addresses.
Just to be pedantic, it's "illegal" to hoard IPv4 or to buy it for any purpose other than using it directly. But yeah, in the real world it may become more financialized than it already is. OTOH if prices keep dropping maybe they won't bother.