I guess your view on the cost of fixing bugs in production vs development depends on context.
Take 2 examples
An early stage startup with a fully CI/Cd pipeline might well decide that is cheaper to fix production bugs since
a) they are really only trying to flip the company to a VC mug and couldn't care less about the actual software
b) no controls on release push and go all the way to prod, who cares.
c) the bugs may never be found, happy days.
On the other hand in a company with Sox-like controls, financial numbers and multiple people involved it a different story
a) bug impacts the user, might be a blocking bug so causing material cost on a user level, many users affected? x times that impact.
b) bug logged
c) bug repro by dev, might need certain data setup so this can be non trivial in itself.
d) bug fixed
e) build, deploy to system test
g) deploy to UAT
g) UAT has be done by users so needs their time so $
h) if release requires an outage a Change Approval board has to approve the release. Board sits one a week has 3 person manager level quorum for approval. $$$
i) release window approved
j) release happens requires OPs, Dev for smoke test and users for Prod smoke test $$$
k) close out bugs.
I haven't even tried to put a dollar number of that cost.
Bottom here here is find those bugs in dev.