Linear has no sense for a scarse resourse: the more you get the more you pay. Linear does not follow that simple principle. So if you really would see people implementing IPv6, then maybe not exponential but for sure not linear
Not even needed to go exponential, just make it linear.
Say something like 10 cent per IP per year on average (or whatever "class" model that ends up around there) : any LIR with less than a /20 will pay less than now, who has allocated something around a /8-/16 will have to rethink about moving to IPv6 (or release the addresses, if they are not using them).
A.
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