I am looking at purchasing an expensive card graded psa 9.
There is a visible black ink dot on the yellow left border. Rest of the card is clean.
Should ink dots be more of a detriment to the grade?
I’m not 100% sure but I think it just depends on the size and location. I graded a PSA 9 1st ed fossil kabutops that was absolutely flawless aside from one tiny black ink dot just above the bottom border. In my experience, factory errors (ink dots, stains, print lines etc) will only keep a card from getting a 10 unless they are very severe.
At the end of the day it’s your opinion that matters though. If you don’t like the card because it has the ink dot then it doesn’t matter what PSA thinks about it. I personally would much rather have a flawless PSA 9 with a small factory ink dot than a PSA 9 that has whitening on the back or a holo scratch or two.
I’ve really wondered this. I bought a skyridge jolteon holo card that had 2 very small green markings on the front of the card. I was worried it was pen markings and I bought a damaged card but when looking online I found several other examples of the card including one graded PSA 10 that had the same exact markings so clearly they were part of the printing process.
This makes me wonder, did PSA notice it and if so why did they still give a PSA 10 of they’ll dock a cards grade based on a printing line? Or did they not notice which seems hard since I noticed it upon a simple inspection of the card after buying it. Really not sure what their stance on ink markings seem.
The card in question. Not a clean round ink dot either, micro smudge evident. Should this really be a 9? I’m on the fence as to whether i should buy it. 
As @chopkins1994, said, entirely up to you whether or not you care about the dot. Buy the card not the grade. Personally if I know it was an issue with the printing process and not some damage to the card, I don’t particularly care.
Usually imperfections like ink dots aren’t given a big deduction by PSA outside of 10s, if at all.