The advice on the board should be checked out carefully. For one, "reportable" transactions aren't as described. Check:
https://fisherpreciousmetals.com/resources/general-market-info/truth-precious-metals-reporting/
for a well-written summary. I also wonder whether your desire to be bulletproof against an IRS audit may be leading you to overpay taxes. It may be that the gift you received was a Gift Causa Mortis - a deathbed gift - which implies a different tax treatment, as if the gold were inherited. The cost basis would then be relatively simple to compute, and much smaller than a usual gift.
I am not a lawyer or tax pro, but if the amount involved is substantial, hiring one or both may be worth it. Their professional rationale would then become the rationale for how you file your taxes, and if the professional is reputable the risk, even if there were to be an IRS audit, is very likely limited to any amount later determined to be underpaid.
I agree with the post that you should pay what is due, but as Judge Leaned Hand said:
"Any one may so arrange his affairs that his taxes shall be as low as possible; he is not bound to choose that pattern which will best pay the Treasury; there is not even a patriotic duty to increase one's taxes."
Best of luck.
