Wholesale is a lower price that is paid by someone who is (generally) not going to keep the item but sell it for a higher price to an end user or "retail" customer. In business, you generally try to sell it for about twice what you pay for it, but this depends on the compitition and the selling price. The profit from the sales is often described as the "profit margin" or just "margin" and is a percentage.
I was surprised to see people state 20% as an average profit and wonder where that comes from given the low trader numbers?
I'm always open to learn more about this business, but from what I've seen so far, the end user price really depends on how much they want the domain and their ability to pay. Here's an example: I bought a .org name here for $5 and parked it. 6 months later I got an offer from a broker at SEDO for $450. I was pretty happy, but I wanted to make sure I was really selling the domain for what it was "worth". I researched what the other main TLDs were selling for ($1,000-$2,500) and said that I thought the domain was worth more. The broker said the offer was pretty good and asked me how much more? I said less than $1,000. The next thing I know he tells me he will buy the domain for $1,000! Yes, I was very, very happy.
Later I found out that the "end user" was a giant telecommuncations company in Germany. I probably sold that domain for 20% of what it could have sold for, and who knows how much the broker told the client it cost...?
So I think it really depends on your knowledge of the industry and the buyer, but also your ability to make a deal. I have no regrets about selling a $5 domain for $1k, but I will try to get a better sense of where the buyer is at next time by asking for more if I have any clue that it may be possible to do that.