I've started trading heavily online again because I have very little time to trade in person, and only the same 5 or 6 people to trade with in person. For the most part, it's a positive experience and one that I recommend. However, as with all trading, you hear ridiculous stories from people trying to rip you off. What follows are the most ridiculous things I've been told which should serve as a guideline both as what you should avoid saying yourself, because you're not fooling anyone, and the kind of crap that people will say to try to trick you into undervaluing your cards or overvaluing theirs. These are things people have actually said to me when trying to get special treatment for their cards:
"It pains me to lose value on cards cause of [condition] when I value them the same." Cards have prices for different conditions for a reason: better condition cards are worth more. You are not losing value on your VG (very good) dual lands because of condition; they are worth less because of condition. If you traded for them at NM (near mint) prices, that's your problem. If you value them the same as NM cards, that is your ignorance. These people have the same mentality as those who want full retail value for cards they sell to our store: you're trying to make money off of me.
In neither case is this correct. In the case of played cards, I'm simply trying to get the cards for the correct price. In the case of selling cards to a store, I'm trying to make money off of my hard work, man hours, and knowledge. Just because things aren't going the way you want doesn't mean everyone's out to get you. Fortunately, people with this kind of trading mentality can normally be reasoned with as they're not actually trying to take advantage of you and simply want what they misconceive as being fair. Just be sure not to sympathize with their position or you can be taken for a ride.
"I had to pay a lot to get these." So? This one (or subtle variations) is heard most frequently right after rotation. The last time I heard it was when I was trading for some shock lands after they left extended. There's not much to this argument either: they bought cards at their peak and now want to recoup that full value because they don't know how to properly manage their inventory. My answer last time was rather curt, but a nicer version of it normally gets the message across nicely: "I can't value these cards higher just because they used to be worth more." This scenario can go either way: the person knows that they're trying to get more than their cards are worth, and now they know that you know it too. They may either pull their cards off the table and try to find someone less informed, or, if you have cards that they're interested enough in, will accept fair value on their cards.
"These aren't worth anything." This one pisses me off more than anything other thing people say when trying to rip you off, and it's also the one you hear most often. It's normally used to describe cards that are a small step above bulk rares (as in playable and popular in casual play, but worth normallly $0.50-1.50), and only used to describe your cards, never theirs. Describing my cards as being literally worthless is a surefire way to have me take my cards off the table, and it's really the only correct course of action. Afterall, these people are not only calling your cards worthless but actually treating them as such in the trade. "Worthless" is not a mean way of saying bulk to them; they will insert these "worthless" cards into whatever trade you're working on and give nothing in exchange.
And now for Bill O'Reilly's most ridiculous item of the day:
I had pulled a foil Volcano Hellion out of someone's binder, because it was one of the last foils I needed for my foil Planar Chaos set. Because it was one of the last ones I needed, I was willing to go as high as $3 on it just to get the set done, at which point I was told this: "I need more than that; that was the foil rare in a really bad box I bought, so I need to make up the value somehow." I don't even need to explain what to do if someone tries treating you like this on the trade tables. (Hint: Physical violence is encouraged!) [Editor's Note: We do not encourage violence. Please see here and here for background.]
Alright, I'm done ranting. Go forth into the world and trade!