I sometimes have the same. As you may or may not know, I collect Pikachus and currently have the largest Pikachu collection in the world with over 800 unique cards.
When I started collecting Pikachus I was only going for ungraded cards (doesn’t matter if they were heavy played or mint; although mint was obviously preferred). I had almost all English regular and foreign Base Pikachus: English 1st edition Shadowless Red Cheeks; non-1st Shadowless Red Cheeks; 1st Shadowless Yellow Cheeks; non-1st Shadowless Yellow Cheeks; unlimited edition ©1999; unlimited edition ©1999-2000; Japanese no rarity and with rarity symbol; Dutch 1st and UED; German 1st and UED; French 1st and UED; Italian 1st and UED; Spanish ©1999 1st and UED; Spanish ©1999-2000 1st and UED; Portuguese 1st and UED; and a Chinese UED. (PS / off-topic: If anyone is interested, I made an article in the past about ALL Base Pikachu Artwork variations that exist.)
But no matter where I looked, I couldn’t find any ungraded Chinese 1st edition, or Korean 1st and UED. Korean UED is very hard to find even if graded, but ungraded is really hard.
Every time I searched for them however, all three smiled at me from the same seller in PSA-9. Their price-tag was therefore also a lot higher than ungraded would be. After little over a month, with the three PSA-9 cards still unsold; I couldn’t take it anymore. And now I look for both graded or ungraded, PSA1 or 10, heavy played or mint. 
As long as I don’t have them yet.
Another example: Somewhere at the start of this year a Pokémon with YOU Pikachu card emerged on YJ. The card was released in 2015, and I hadn’t seen a single one for sale ever. So obviously I was pretty siked. Placed a bid, got outbid so raised, and raised, and raised, and… Still lost 
It ended at 135,000 Japanese Yen (~1,2k USD). Bummed I lost such an amazing card (I mean, just look at that artwork:
),
I went on with my life. Less than a week later another one popped up for 95,000 buy-out. It was gone within an hour, before I even noticed it. Then another one popped up, so I placed a bid. But then another one popped up, and another, and before you know it more than 10 were available for bid/buy-out. Some even with a cheaper buy-out price than the bid I had placed on that third one… But since I used the middleman service Noppin, I couldn’t cancel my bid anymore… 
My max bid was 77,777 and I ended up winning it for 77,000 (~700 USD). This was excluding shipping costs, middleman service, and import fees on arrival, which upped it to little over 1k USD.
Now you can still find them on YJ and eBay for around 200-300 USD… If only I was a bit more patient, for just 1 to 1.5 months, then I could have saved more than 650 USD…
Ah well, we can only learn from our mistakes I guess. And I haven’t regret buying it. The artwork is great, and it’s a great addition to my collection. And it could have been much worse if I had won that first one. 
And what if I had lost this third one, and it would have been the last one put up for sale in years? Then I would have been so pissed on myself for not going a tiny bit higher to secure it.
So no, it’s a bit annoying they are now widely available for 200-300 USD while I have paid 3 to 5 times that amount, but I don’t regret it.
The future is what matters, not the past. We can only learn from it, to make the present and future better for ourselves.
Greetz,
Quuador