Lol, all the time. I have over unique 1100 Pikachus, and I can’t be too picky about price or condition when one pops up I don’t have yet. 
So I usually pay like 20-50 USD for cards that are probably worth about 10-20 USD.
There are however two cards I can name for which I overpaid quite a bit:
- 175/XY-P with Event Organizer stamp. Bought two of them for 1600 USD. Halve a year later they were for sale every now and then for 150 USD each.
- Pokémon with YOU XY-P promo. It hadn’t been for sale for over 3 years, so when the first one popped up everyone bid on it. I eventually lost it, and it went for around 135,000 Japanese Yen (~1200 USD). Second copy emerged just a few hours later, and was sold for about 95,000 Japanese Yen (~850 USD) within a few hours. Third one that popped up I placed a bit on of 77,777 Japanese Yen. But in the next two days ten more popped up, lowest being around 55,000 Japanese Yen and in better condition then the one I placed my 77,777 bid on as well. I ended up winning it for 77,000 Japanese Yen…
The one time you want to get outbid, you win it at your absolute maximum. Including middleman services, shipping costs, and import fees, I paid around 950 USD for it in total. Considering halve a year later (and now still) they are available for 250-350 USD, I should have been more patient. Then again, if those were the only ones that would have popped up, I would have regretted it for not going higher to make sure I win it. Ah well, you win some you loose some.
Greetz,
Quuador