If we want to talk RSA the engineering journey from factoring 21 to 35 is big, because it requires creating logical qubits with error rates that we are only now seeing companies report. But the engineering journey from 32 bits that are tolerant enough to run a factoring algorithm to doing the same with 4096 appears linear in engineering cost is what I am claiming.
For RSA specifically the resource have come down. I am not yet up to date on this round of papers however the 2024 result https://eprint.iacr.org/2024/222 had it down to n/2 + O(N) logical qubits.