On the other hand: Perception of change might not be linear but logarithmic.

(= it might take an order of magnitude of improvements to be perceived as a substantial upgrade)

So the perceived rate of change might be linear.

It's definitely true for some things such as wealth:

- $2000 is a lot of you have $1000.

- It's a substantial improvement of you have $10000.

- It's not a lot you have $1m

- It does not matter if you have $1b