unfortunately, a lot of cards gain most value in psa10. Some cards are worth not much in a psa9 and then suddenly thousands in a psa10
In general my biggest come ups were from goodwill snipes in years past on loose binder collections
but thinking about loose buys, some ppl simply dont grade cards and follow NM price trends. From this I can think:
The pokemon center lady I found insider a binder that i paid 71 bucks for. She was in perfect condition. After grading its now worth almost a thousand bucks
mew gold star i got in a binder that i paid 295 for… it graded a psa9 (havent check price value in a long time)
Charizard XY holo… bought for $80 raw at the time… graded psa 10 for ~$1,500
stormfront zard i bought 5 years ago as a psa “contender” for a few hundred bucks. Today its worth around 10k?
Tbh, I don’t think I’m the right person for that kind of stuff. I simply got (very, very) lucky.
In fact, when I bought them, people in Discord even mentioned I overpaid and should have waited. Halve a year later, the prices were roughly 800 for Lillie, 500 for Acerola, and 200 for Guzma (~1500 total).
I made some screenshots of those Discord chats at the time
I simply bought the EBD promos at the time to complete my FA Supporter/CHR collection. Likewise with the PSA-10 The Masked Royal that’s mentioned in the same Discord snippets (which I bought ‘way overpriced’ for 3.4k USD and is now also worth north of 60k USD). I’m a collector, not an investor or flipper. But in the case of the EBD promos, I simply took my chance to change my life by buying a house when the opportunity presented itself. I must also admit I’m very happy there were S. Chinese replacements for the same artwork. I’m not sure how I’d feel about breaking up a complete collection. For that kind of money, I’d still had done it, but it would have been a tougher decision. I’m a completionist, and a bit of a perfectionist as well tbh, and I also almost never sell anything from my personal collections.
Anyway, if I’m ever in need of money again, I can buy the S. Chinese The Masked Royal and sell my Japanese PSA-10 copy.
Following with what PFM said and using an example where years did not pass between acquiring a card, grading, and selling it, here is another example.
Hyper Metal Chain Deck FA Dialga EX 019
I traded for the card at World’s 2023. My side of the trade was a PSA 10 Bronze Victory Medal Pikachu 031/L-P ($150). The vendors side was the Dialga FA and a Damage Design pack of card sleeves ($60 in value).
I bought a PSA 6 copy of 290/XY-P Ash-Greninja EX off PWCC for $31. Waited about a year and cracked it to resend to PSA. Happened to luck out and it came back a 10.
They were selling for about $1200 when i got it back. Havent looked up current prices.
I bought a raw Secret Wonders Charizard holo locally back in I believe 2020 for like 30usd … Graded it using Bulk service level at PSA, it graded PSA 10, and I sold it for 6000usd
My sale of the card (under market value) took place after 1 of these slabs in PSA 10 sold for 10k or so on PwCC back durinf the Covid bubble. Biggest percentage W in my hobby life…
I pulled an Erika´s Venusaur back in 2015 from a 15 euro Gym Challenge pack. Graded it last year in a 10. It´s worth 1K+ now, so that would be 1k profit, however, I had to wait nearly ten years for that.
Perhaps @pfm is right in that most people’s biggest increases in value have likely come from the passage of time and changing of interests rather than receiving a specific grade!
I welcome anyone that has a post in this area of interest to reply with their before and after whether it is before/after grading or a purchase in the past that has appreciated greatly. I realize this opens things up a lot though and gets less scientific but nonetheless its still an interesting topic.
Here’s mine, though it doesnt compare at all to some of the others that have been posted
13th birthday of October 2013. I had just gotten back into pokemon and XY came out on my birthday. For Christmas, I wanted some cool cards that I used to see my older cousin have. STG, my mom went on ebay after asking around and spent $200 on a collection someone was selling…
PSA 9 Base unlimited Charizard
PSA 9 base unlimited Blastoise
PSA 10 Ancient Mew
PSA 10 Shadowless Venusaur
I kept them and had them sitting under my TV in the living room for years and I forgot about them. When Pokemon came back into popularity in 2020, I was in college and getting back into it. For some reason I remembered I had cards and it took a week to find them. I nearly had a heart attack when I found them and realized what they were. In total, I sold them for $10,000 roughly during the boom and used the funds to jumpstart my collection since I was a poor college student. Best decision ever.
Hmmmm, not sure I have anything super impressive to share.
Bought a unlimited blastoise from an lcs for like $50. Subbed shortly after i bought it, $18 July special in 2022. I think there was around 20 cards in the sub. Came back a psa 8, sold it for like ~$250 with a canadian seller on instagram
Also got a 2019 players ceremony off ebay in april of 2022 for ~$400, graded a psa 10 in same July special order. Seems to be around $1000?
Blaine’s Charizard Japanese, bought off a coworker selling his collection for $50, same time and sub as other two, graded a 9, looks to be around $200.
But in the case of the EBD promos, I simply took my chance to change my life by buying a house when the opportunity presented itself. 
I must also admit I’m very happy there were S. Chinese replacements for the same artwork. I’m not sure how I’d feel about breaking up a complete collection. For that kind of money, I’d still had done it, but it would have been a tougher decision. I’m a completionist, and a bit of a perfectionist as well tbh, and I also almost never sell anything from my personal collections.
$7.89 
