When you say "trade," are you asking what you might expect a retail store to offer you in trade when buying? If so, I would think somewhere in the neighborhood of $200-275.
Why?
You can buy that bass online at Carvin for about $650. Typically, used stuff (unless there is a huge popularity trend) sells in the range of 60-65 percent of what you might pay new. So the actual used sale price is about $400-425. Maybe a bit more in a high-traffic retail store, or a bit less in a private classified type sale.
But, when trading, depending on who you are dealing with, a dealer will offer you roughly half or a bit more of what they can expect to sell the bass for to you in trade value. So, we are talking $200-275.
You also forfeit a bit of your right to haggle when trading. Just like with a car, they may offer you more in trade, but they get it right back by firming up on the asking price of their piece.
As usual, you are better off trying to sell the bass using local or online classified or even ebay and then making a cash offer on the bass you want.