The cost per transistor is going up because the latest nodes require too many process steps. An older node might require 90 steps, the lastest nodes require 900 steps. Every step requires a "tool" and every step has a chance of yield loss. The transistor is getting harder to make faster then it is getting smaller.

The new EUV steppers with soft x-ray wavelength can do in one shot what took 4 shots with 193nm ArF tools. And for each shot you have to apply, bake, develop inspect and strip the resist. This was supposed to help but the EUV steppers are so expensive it is kind of a wash price wise.

> Isn't this just because of overall chip shortage?

AFAIU, no. The basic problem, again AFAIU and I'm not an expert on this topic so take with a grain of salt, is that while the marginal cost of each transistor might still be less than at the previous generation, the R&D and capital costs have grown so immense that once you amortize those costs over the stuff produced for the lifetime of that process generation you end up with a higher per transistor cost compared to the previous generation.

> Any source for this? Anything I've saw contradict that.

Just search the web for articles about the breakdown of Dennard scaling, plenty of stuff to read on the topic. Even wikipedia mentions it https://en.wikipedia.org/wiki/Dennard_scaling