I would say nothing. And I don't mean that spitefully at all. But I have personally registered more than 10,000 domains; and by now I have a fairly good idea of what domains will and will not receive purchase offers -- and at what amounts. Too many people have registered too many "3d" domains. Mostly these products do not exist yet. 3dPhone.com would have some value to someone who wants to speculate on the future of something called a "3d phone". But nobody I know makes or uses a 3d phone. Meanwhile, 3dPhoneWorld.com is definitely a big step down. There are so many other options that a buyer could choose instead: 3dPhoneClub.com, 3dPhoneStore.com, Buy3dPhones.com, etc. And the buyer will choose the cheapest option, which means you'd have to lower your price farther and farther just to compete with everybody else. Of course, that's all hypothetical. 3d phones aren't real yet, as far as I know. If I'm wrong about that, ok. But always think about alternatives to your domain. If there are a lot of alternatives, then the domain's value is reduced a lot.