What kind of website is this for? I think that would help some. Also I usually buy the most common tld for the domain but why would you buy all?
It looks to me like the OP wants to sell domains rather than just buy them for his/her own web site.
It's not uncommon for multinational companies to register their name under every TLD available (i.e., for trademark protection purposes) so there is certainly a market here... the only problem is that the corporate market is fairly firmly in the hands of half a dozen or so major players (Markmonitor, Ascio, MelbourneIT, CSC and a few others) so I don't think it would be easy for a newcomer to break into this market.