Back when silver was $14-$15 I put a snipe on a tube of American Silver Eagles.
I had only bought 50% pre dec up until that moment, mostly in bulk. Never small numbers of coins and no 999 stuff.
My bidding spreadsheet was set up to work out how much to pay for 50% pre dec so I had to make a hasty formula alteration in order to work out how much to bid. I used to bid spot minus postage. Back then I actually won quite a few.
The calculation looked a bit steep but I had never bought 999 before and figured that it would be twice the usual price of 50% and 1oz coins would weight more than shillings so maybe that was why.
I won the auction!
Well under my calculation for spot.
Something was obviously wrong, I went back and redid the calculation...
In my original haste I used the wrong cell in my formula, instead of the current spot price ($15) I used the cell next to it, the number required to multiply the ounces by to get grams, 31.1.
I had bid nearly double spot, not surprising I had won it for below spot.
At this time silver had only gone up a couple of dollars in the last few years, it didn't look nearly as volatile as it does now. It would take years to make it back on the small gains I was making on below spot pre dec and it wiped out a lot of my gains.
I hid them and vowed not to look at them again.
Took a good 2-3 years before silver picked up enough to wipe out that loss, but it eventually did.