Box looks good in the pics but that really doesn't tell you much. That box is also not going to trip the trigger of a young tech so your competition for buying is slim. One question I always ask is have you had a lot of interest? Often they will say some low ballers or no not really. That sets the stage for your offer.
The other thing you have going for you is not many people have 2 to 3 grand in cash to make a deal. Trust me,,,,,,,,,,I know this from both sides of the equation. If the box is nice and the drawers work well, I would offer no more then $2000. And see what he says. As far as waving cash, that would do nothing but piss me off as a seller and a take it or leave it attitude would cause you to be shown the door. Now saying cash today, right here and now, is a more acceptable ploy. You never want to denigrate your seller or buyer. Far better to have them feel you are making your best offer whether buying or selling. A soft approach works quite well for me whether buying or selling.