set out the thread well, and dont realistically expect more than 50% of whatever you paid for it originally. this hobby has shocking depreciation and its only greed that causes these problems be it greed on the part of the buyer or the seller.
for buyers its simple: if you want something, and the price is fair, pay the price. haggling is one thing, being an idiot and losing a potentially good deal is another. if you dont have the money but you want it, well tough, the amount of nice things i've seen slip through my fingers cos of a cash flow problem. if your gonna ask someone to wait, then at least either be serious, or as i preferr tell them if they get an offer sooner not to feel guilty about selling it.
for sellers, as i said above, dont realistically expect more than 50% of what you pay for things [unless some serious research proves you can expect otherwise, but for the love of god dont trust an ebay search, just cos someone is offering a buy it now price on summat dont mean its accurate, or that it will sell at that price], out of everything i've sold i think the most i've made back is 60% of the original price. and if buyers give you trouble, well hello my block button, unless you need money in a hurry then patience is the biggest virtue you can have, and if you do need money in a hurry, well selling things less than they're worth is the only way you'll get it.
and that concludes hamsters sagely advice for not being an idiot when it comes to buying/selling