What Is Your Most Expensive Philatelic Purchase?

I recently bought something that I paid way more than I should have and it made me curious about people on this site and their collections. I was wondering, what are your most expensive philatelic purchases? I don't care about how much it cost exactly, you will know that, but I am curious about items that people here have bought that they think cost them a lot and if they felt it was worth it, as well as what drew them to pay so much for the item in question. I am sure a question like this has been asked before.

US Scott #1612 full sheet is probably my most expensive purchase. I've bought (2) of them.

I've never regretted paying too much but have regretted, frequently, paying too little.

A gutter block of Confederate #8 with position 1 with the major double transfer.

Scott U.S. #1 & #2, no regrets

@germania can you elaborate?

Yes, and some took quite some time to pay off. I still own each such item and glad to do so. Additionally I want to point out that "expensive" meaning at the time of the purchase how much I made and how much I could scrape together to spend defined "expensive" at that moment. Thus, $20, $200 and $2000 could be expensive purchases at particular times.

I would buy an item at what I thought was a bargain price but after some time I would see it was not particularly well-centered or see some other flaw.
For items I paid more than I thought I should have, have invariably been the items that brought the most joy.

So don't worry if you think you overpaid; in the long run it doesn't matter. Years from now you will probably enjoy the item even more than you do now.

About 10 years ago I paid an insane amount for the stamp in my profile pic. No regrets as only 7 are known to exist.

I just got one which has the number 44444 at the bottom, should I be worried?

US Scott 2915C Plate #88888 used?

U.S. #1 and #2. No certs and no regrets.

No, but close...Scott 2915C Plate #66666 reverse die cut 12 x 11 used.

Unless I am missing something, I see Scott does not have that listed, specifically the 2915C as a reverse die cut. Any idea why? For example they choose not to list reverse die cuts at all.

Edit: Thanks for the great photo.

No idea why Scott doesn't list this specific stamp or any of the reverse die cuts. There is a Special Feature on the 32¢ Flag Over Porch self-adhesive coil stamps in the 2021 Scott Specialized Catalogue, but the value for this specific stamp is just a dash.

The rarity and value of the stamp was derived from the Plate Number Coil Collectors Club PNC3).7 total stamps reported, 6 used singles and 1 on cover, found over the last 29 years.

It is only expensive if it exceeds or closely approaches your financial comfort level and that is different for everyone.

For myself, I have only regretted purchases where I had a severe due-diligence deficiency and that only occurred in my early days. Emotion overrode common sense and things may have been purchased without certificates and/or external to my knowledge range.

I have to say that given the long history in philately of shysterism and skullduggery it is a place to proceed when purchasing with extreme cynicism.