um, i was addressing the poster above me, who was saying that since all the players were dedicated enough to travel to the big event, they should 'know' what cards were worth...
'mom
I don't think it's unfair for me to assume that if a kid is running multiple Magnezones, Emboars, Donphans, and Machamps in their decks, as well as Collectors, etc, that they know what the card is worth. They didn't just pull all of those cards - they had to have traded it or paid for the card (or their parents did). I know that locals will be there, but I think at least 50% of the players there will be from out of state considering the size of the event.
Whenever I went on ebay to get a card that I needed for my deck (when I was a kid), my dad would subtract the money I spent from my allowance. So I knew exactly how much something was worth. I sell a LOT on ebay and you'd be surprised how many people leave me feedback that says 'my son loved it!'.
I'll be brutally honest though.. when I trade, I trade for profit. I don't start my career (I love how fancy that sounds) until the middle of July so I have a lot of time on my hands. That means I spend a lot of time on ebay, looking at completed prices, watching what troll and toad does with their prices, etc, to the point where I have the value of all major cards in this format memorized, as well as general values for some older collectible cards. At league, whenever my friends are trading you can hear them calling me from across the room and giving me a list of cards for me to write down the prices for because they're trading someone lol. I also do a lot of speculation. Back in April I figured that Magnezones, Pachis, and Shaymins were all going to be big, so I hoarded them like crazy, trading for Magnezones valued at 15, shaymins at 3, and pachis at 5. In the last 2 weeks I've been selling all of them on ebay for humongous profit. I didn't expect RDL and Cleffas though.. missed the boat on those unfortunately. I'm a business-person at heart. It's what I got my degree in and where I'm going to work. I love taking advantage of 'market failures'. I do a LOT of research on card values, and if someone isn't up to date on their values, then that's unfortunate. I think this touches on what you were talking about lostjackal, with fluctuating prices, but I don't find myself in the wrong for trading for Pachis (for example) at a $5 value because the other person didn't take the time to look at what prices are now. It's not insider information; it's available to everyone. If I keep better track of it than someone else than I will reap that profit since I spent a lot of my time keeping up to date with the info and they didn't. To the victors go the spoils. This paragraph is more when trading with teens/adults by the way, before anyone throw me over a bridge.
As a note, parents can be pretty annoying sometimes. The other day, I was trying this kid at league for 2 Golbats. Just golbats, worth $.30 on troll and toad. I was offering him a holo/rare/reverse holo for them and his mom kept interjecting and it even annoyed her kid. They were two bleh uncommons! I ended up not trading him because it was too much of a pain.. ended up getting them from my league leader for $1.
As for karma.. my karmic universe is doing just fine. At battle roads, a player couldn't afford sleeves and was going to have to play without them so I bought him sleeves. I've paid for 2 different kids at pre-releases because they couldn't afford the whole price. I'm not an ogre, I promise, lol.