Until you have a good idea about what some of the regular buyers might bid on it, you are in dangerous territory.
If you value the sales potential at $600 you would be safe bidding $400 but it might not pan out the way you think if you get it.
If the other's see it the same way and they are happy with only $100 profit then they might bid $500.
On the other hand if they are all cheapskates and only bid $150 to $250, then you might get it at $400.
******
Until you know what the competition will do you could always bid lower, but chances are you will be beat by someone.
When bidding, put down an odd number like $399.00 or $401.00. Most people will bid more even numbers like $400, $410 or $415. Most places won't allow bids like $401.76.
I have lost several of these bids by $1.00. It happens and there's no way around it.
Good luck and try to keep good notes on what happens and share it with us.