All the time
If I may offer some advice on the negotiation....
The way it works best, IME, is to set an asking price and a list of stuff included. When people call, they may ask if you'll take something less, and to that you respond that if they come to look at it and want to make an offer, that'd be fine, we can discus an offer then but you are not lowering the price for someone who hasn't even seen it yet. "Until I have cash in hand for it, it is still for sale at the asking price."
If someone says they'll come look, you still tell all callers that it is still for sale. And always get the phone number of the person coming to see it, "just in case you have to step out" while waiting for them. You might want to tell the callers if someone is supposed to be coming to look at it, then take their number in case of a no-show. Or have them call back in a few hours.
You do not want to have people work you down by calling and getting you to knock the price down before they even get there, and then start haggling again when they get there. You should not be "throwing in" stuff during the negotiation, unless you had already made this concession in your head and knew you were willing to do it.
For a lot of people it is not so much the price but the bargain they got. I'll see a 10 gallon tank with a stand, hood, rocks and airpump at a garage sale for $5 and I'll always ask if they'll take $3. If they'd priced it at $10 I'd offer $5. Why pay $10 for something if you can get it for $5 just for asking? So, don't let the bargaining get you down, just know that you need to find out where you are going to stand pat, even if it means the lost sale.
There are a lot of people who are just toying with the idea of a new tank, they are jcalling to see what the market price is for this tank, or maybe they may want to sell their own tank at that price, they want to know whether a used tank at that price is likely to include certain equipment. They may still be wondering if they have room for it. Sometimes they are not very serious and just forget or get busy.
