Hmm, I like to try and complete sets, I just find the card interesting as I've never come across, or heard, about something like this. Cards with these marks, how much do they usually go for, or are they just the same price or lower as if you were to buy the card by itself?
depends on who is buying and for what purpose... as in any other tcg hobby. i don't even have to play pokemon tcg to know this.
but for the most part (unless you find someone who is looking specifically for scrap cards for some reason) you're going to get a bit less lower than average... even from just players of the game. because competition judges aren't too keen on anything on a card that can 'mark' it as a deck predictor. unless that person uses card sleeve, then they might give the same value, as they're not looking to collect, but only for pure trade value...
...and that's the problem when it comes to this: people looking to play the card will only be looking to trade card(s)-for-card, usually. exchange of money is rare (and sometimes banned in shops... local shop of mine has cash-for-card trades banned between customers... people do it anyway, and i don't think the guy batted an eye when i traded a wii for half a deck of rare MtG cards back in 2011 lmao)
as for collectors, most of them want their stuff as close to mint as possible... to preserve. cards with potential judge markers (it varies by judge, but a lot of them are incredibly anal) and cards with ANY damage whatsoever aren't really sought after over their unmarked/undamaged counterparts. and collectors definitely want them in the best condition possible... even holofoil curling is unacceptable.
your best bet is to find another player, who plays exclusively with card sleeves, who will shrug off a bit of damage, then ask if they're looking to give a bit of cash for cards. just don't expect anything higher than the low selling point on tcgplayer.com from most, if they even trade cards for cash in the first place))