The 1080 and the rumored 3080 are not the same architecture: they didn't just get die shrunk.

For the same number of SMs, you're also paying substantial area for the tensor cores, ray tracing acceleration, independent thread scheduling, different I/O to support memory technologies, more NV link, larger caches, etc. That stuff didn't happen for free.

A simply die shrunk 1080 would have had more TFlops than what we have, but it wouldn't be as interesting of a product.