XXX in cash or XXX in trade???
 

Ex:

$250 in cash or $300 in trade.


What's the logic in wanting more if the seller trades with buyer instead of straight cash?

Context is your friend.

With the negligible amount you've provided, I would imagine the seller would encourage a trade because it guarantees him a profit on the sale of another product. If he offers cash, there's nothing stopping the "buyer" from taking the money and running.

Markup, they don't lose money in trade, they just keep more of yours.

Ever scoured CL or any other classified ads?

Everybody thinks their shit is worth more than it actually is.

If you give me $250 in cash, I have $250.

If you give me your item that you think is worth $300, I probably have about $200 in value.

Even if your item is actually worth $300, I still have to make another transaction to realize any spend-able capital, and my time is worth money.

Precisely what I was thinking.