This is a great case still in great condition. 
I would like to offer $5 for it.
That is too low for this case. I would like 25
Are you willing to negotiate on the price?
If you buy today I would be willing to go a bit lower
I would be willing to buy it right now, if you are willing to accept a bid of $7.
Would you go up tp 15?
I would consider $10.