At least Undeveloped does a lot to try to get buyers to pay. They actually do call the buyers. I doubt Sedo ever does that unless we are talking about very large transactions.
They certainly do, I can vouch for that myself also. Maybe other places do also but Reza and Simon both worked on one very difficult prospect for 4 weeks until they asked me what I wanted to do. And they both personally contacted me with regular updates. Other places give a system update or a generic response - you dont know if a human is even behind that message.
Others have said, its a numbers game. It is. Here's to hoping that the numbers are favored toward sales and not deadbeats
I also think that in certain cultures its OK to negotiate, even come to an agreement and then walk away anyway so I understand that some folks see no issue with this. My immigrant grandfather used to embarrass me when he would try to talk down the price of fruits and vegetables all those years ago when I was a child and would go to the grocery store with him. For him that was the norm, the custom. Sometimes he'd haggle and even get a manager to lower the price and then he'd decide he didnt want or need it. But like I said earlier, that grocery store had other Apples to sell while my grandfather haggled the price of them. He didnt hold that one Apple in his hand and take weeks to decide to pay and then not pay.
I still believe something can be done to mitigate these instances of prospects going cold.
Simply asking for a deposit will shake out 95% of the tire-kickers (as I call them) - whatever their reason is for walking away. If these folks are serious buyers then plopping down 10% for $1,000+ USD prices (or a fixed fee for for under $1,000 USD) would be no problem for a a
serious prospect. They know that holds the domain name while they get their funds in order and it also goes toward the purchase BUT they lose that deposit if they decide 3 weeks later they do not want it. Sometimes it takes a while to get departmental approval to purchase large ticket items. I understand that and I have had that happen. I've had one sale take 6 months due to red tape at the corporation. I am sure others have had this experience too.
Of course, there can be circumstances where they could get their deposit back but that would have to be extraordinary and documented. One time I had a non-paying prospect at Sedo, he bought a domain on a Friday night buy-it-now, didnt hear from him for 3 weeks until I started to do some research and found out that he was killed two days later in a traffic accident. Life happens, deposits could be refundable in extraordinary cases like that, financial problems, etc.
Just my opinion based on experiences.