Its really worth as much as someone is willing to pay...see if there are business's out there with l-l or whatever in their name.
generally L-L.biz is worth just the reg fee, but if the name is good its worth good money. eg : A-Z.biz B-B.biz - Business to Business B-C.biz - Business to Consumer
Excellent minimum price guide for 3 character domains: http://www.3character.com/priceguide.html I'm afraid it values a L-L.biz at $10 though......... Not a fool proof guide though, you never know what people will pay for sure!