Why do people set a higher trade value in private sales?

[guitaardvark]

A lot of the time, I'll see an ad that says something along the lines of "Price is $x, but trade value is higher."

It makes complete sense when a store does this; they'd rather give you store credit to incentivize you to spend your money with them. I really don't understand the reasoning in private trades though, since both parties can inflate the prices due to "trade values," which seems pointless.

Can someone help me understand this?

 

[Thesius]

Because cash is king/higher priority for them.

 

[guitaardvark]

Because cash is king/higher priority for them.

Got it. So basically the original seller is the only one who can claim the inflated trade value. Love the username, by the way.