I know there are some similar topics, but I want to limit this to cards that you wanted for your pc, not ones that you now see as ones that you miss b/c of the "jump" in investment value. Here are mine.
1. About 5 years ago there was a beautiful SGC 88 Aaron RC on eBay razor sharp pack-fresh maybe a little o/c top to bottom for 2K-ish with a big seller like Probstein. Month after month it remained unsold. Eventually, it sold. My thought: "Well, I can't afford that. Only have money for a 5 or so which leads to....
2. Same time frame a very nice centered "5" on eBay of Aaron RC eBay. 1K, asked the seller if he would take 900 or something. He says something like $950. I think about it. Email him eventually but the card is sold. At this time Aaron 5's sold for around 1K. Now I would pay x2 or x3 for this one
3. 1953 Bowman Color Mantle PSA or SGC 60 EX. One of those cards that was dead centered and greatly exceeded the grade in terms of eye appeal. Was on eBay for a while a couple hundred above vcp avg ($1100) or so didn't bother. Saw the card at the Cleveland national a year or so later but again, didn't want to make an offer, as it was a bit above average, plus I didn't want to spend all my $ in one place.
4. 1952 Topps Mantle PSA 5. At a shop that tends to sell things at high retail value, so usually just buy supplies, etc. About a year or so before the huge run-up on Mantle RC prices, he had a PSA 5 EX 52 Topps that had great centering image etc, just a small edge bump modest wear on corners. Was asking 20K. I thought that actually not a bad price. I had enough on my CC to make the purchase but of course didn't pull the trigger. A few months later of course the card was gone...
5. A high grade SGC 88 NM-MT Clemente 71 at Philly show a few years ago.
Again, share your story not so much the jumps in price that may be a factor but more so on the card that you hold dear that is not in your pc!