Interestingly I just checked for my keywords in Yahoo and I have 7 of my sites listed in the top 40 ( 2 pages & inc no.1 spot :-D ) and of these sites 4 are non-hyphen and 3 are with a hyphen. Listing 21 (top of page 2) is a hyphenated .biz and others are .com, .net and .org - my conclusion is that hyphens and "lesser" extensions are not hurting my Internet search engine exposure!
Domain-sales.biz probably won't realize it's value here because of reseller prejudice, but sadly because it's all about domain sales its target is to the reseller market so probably in the range of $25 - $50 - better to develop it and use it yourself or maybe sell it later.