Absolutely an interesting thread!
I've been revising/updating estate planning, so learning a lot about taxes of all kinds. Some that have posted, are quite knowledgeable, others, not so much, concerning bank business/forms that they file, things that require bank to make report, etc. Even when gifting to family members, in 2023, if giving away more than 17K, each person, you will need to file a 709 form with your income tax forms for that year.
Many don't realize the records the bank keeps/files/reports, concerning your expenditures, of a larger amount, such as more than 10K in a single day. My investment broker can move money around, keeping off the skyline, more so, than my banks.
In any case, if the OP actually managed to get a buyer to hand over 45K in a briefcase, the buyers bank will have a record of the cash payout. Many banks will want a few days notice before they will hand over 50K of your own money in cash. Banks do not have the huge vaults full of cash, that many think they do.
Jerry