While most sellers assume down is the only direction a price negotiation can go, that's not so...
Anyways try something like $250 or even $500 to start...
If they reply with something like "you're crazy", then likely they're not interested in buying it for anything worthwhile.
If they reply with a counter offer of say $200 or whatever, then likely they're serious...and obviously so, if they offer the ask.
Even if they meet the ask, that doesn't mean the negotiation is over...instead, now that you have a bonafide offer, you can either accept it, if you truly feel that's the best you can possibly do...OR stall things a bit and solicit other offers...then at some future point respond back with "accept" -or- indicate that a higher offer has come to your attention and negotiate from that new price point.
It's late and I'm rambling, but hope the above makes some sense...setting an ask price doesn't automatically lock you in so to speak...not setting an ask, while common, isn't the best way to sell in my view except in instances where one isn't motivated at all to sell and/or there is unusual amount of interest in the asset, though even in those instances setting a "floor" can be helpful and often can drive prices higher.
Help this helps
Ron