I've got some observations, comments, and questions about it - and it'd be interesting to hear your thoughts about it. I would've posted this in the sales forum, but there's no discussion forum there like over at Audiokarma.
I'm an experienced seller; with well over $10,000 in sales of used stuff and probably close to 200 individual transactions.
1. Why do people insist on removing their asking price from a listing once an item is sold? As a buyer and seller I find it invaluable information - there's a reason Audiogon makes you pay for it. Do sellers want to keep others from seeing how much their gear is worth? I just don't get it, really. I'd be interested if anyone had an answer for this.
2. Big, clear photos sell expensive items or those very sensitive to condition. Cameras, lenses, and other optics are perhaps the best example of this. I can't tell you how many hundreds of dollars more I've made just by having better photos than 99% of other sellers, and accurate descriptions to match. Items in worse condition will sell for more than an unknown condition item if the buyer knows exactly what he/she is getting.
3. It astounds me that people are still so resistant to international shipping. Anyone who has done at least a few transactions will realize that with proper security measures (no new bidders on eBay, avoid shady deals, etc.), the benefits far, far outweigh the drawbacks. Simply by requiring a minimum of 10 feedback - and more importantly, making sure that the bidder has left good feedback for others (negatives given are often a sign of a difficult buyer) - you can weed out 99% of the bad guys. This is another area where I've probably gained hundreds in sales - about half of my big-ticket items go overseas. It's not like shipping internationally is hard - PayPal even does the customs forms for you now! All you have to do is fill in a few fields and then it'll print just like a normal shipping label. Take it to the post office, have them sign the forms, and you're set. Add insurance (at the post office), of course, and for items $250 and above (PayPal's limit at which signature confirmation must be used), insist on Express International shipping instead of Priority International. Express requires a signature, and insurance is much less expensive - so in many cases it hardly costs any extra.
4. Get a postal scale. Seriously. They're about $40 and can run off a 9V battery or a wall wart (use the battery). You save money and time on postage, since you can do it all with PayPal now. You get free tracking with the USPS this way. By the way, USPS is always (99% of the time) cheapest for a given shipping speed for anything within their weight range. Since they provide free boxes with Priority Mail, it's a no-brainer to ship almost everything that way. It's easily the best value service out there as a result, especially since your buyers will love it when it only takes 2-3 days to receive their item.
5. Good eBay alternatives are far and away better, and have just as reputable buyers and sellers. Astromart, Audiogon, Head-Fi, Craigslist (well, reputable here is a matter of meeting the seller/buyer), heck, even Flickr (you're not supposed to sell stuff there but it's possible anyway) are great. I don't end up on eBay nearly as often anymore - it's my last resort for selling stuff. I'm sure others will agree with me.
6. While the forums here at Head-Fi are generally amazingly well organized, the classifieds here are extremely hard to navigate. They're organized the same as the rest of the site - but it just doesn't work well. The search function is very limited; the categories are limited; and separation of sold vs. still for sale vs. wanted postings is horrendous.
I probably go on for hours, but I think I'll leave it at that for now. Whaddya think? What's your experience buying and selling? Why do people go out of the way to delete the asking price on sold items?