So, This is a Premium domain at the registry. More reason to accept the E2,000. I don't think your ever going to see the 5k that you want.
Might be worth you exploring the .BIZ history before it fell over a cliff. Don't get me wrong they are two very nice word term except for that dot in the middle. In this internet world the assumption is made your dealing with a Business.
Sure we all do have to use an extension, I can assure you businesses would rather they were Not there and they had full control of a domain term. but, that's not the way things work. So keep your extensions well recognised and short.
Did you actually reply to that offer with your counter of 5k or are you just trying to get the domain in a discussion thread ?