Excellent name! High $x,xxx for sure, but I'd be looking for a proper end user that would pay at least low $xx,xxx.
Great domain! If you have no money then selling it for $20k is a good deal. If you don't need $20k and can afford to wait for as long as it takes to eventually find another buyer willing to pay even more then no, it's not that brilliant. Fair, but not brilliant. Edit: For that kind of domain at those kind of prices, you really should have it professionally appraised. Sedo will do it for you for a fee. They also offer a brokerage service.
Hmm. That's a tough question. Y'see, a domain is only valuable if there is someone to buy it. They are often middle-men or brokers for a final client so although the final selling price of a really good domain like yours might be in the mid-range $xx,xxx ballpark, that figure is only achieved by the brokers, not your average domain speculator like you and there is probably only one final client, i.e. one buyer at the end of the day. For example, say this was the final client: http://www.oxiclean.com Code (markup): They might be the only buyer who wants to buy the domain and you will have been approached by a domain broker acting on their behalf. Do you follow what I'm saying? $20k is a fair offer. Holding out just because you hope someone else will come along and offer more might be holding out for nothing because the end-client will have moved on to a different brand strategy. I really can't urge you strongly enough to seek professional advice and assistance with this.
Low $xx,xxx - Mid $xx,xxx to an end user. If this is your domain, congrats! OXI could stand for a lot of things and would be a great domain in the drug niche. Of course, you could try sell the domain to OxiClean like someone else suggested.