The answer is never. Never. You always negotiate. I have a good offer in with a local listing company that prefers that its clients respond to offers. I made the offer this weekend. My clients offered $190,000 on a $200,000 listing. Today I received a message from the owner that while she appreciated the offer, she was not going to respond. Seriously?
Always respond. Even if you consider the offer well below your tolerance level, respond. I have even had a seller respond back to a low ball offer at $1,000 below list price, knowing that they would go lower. This sends a message to the buyer that we want them to get serious with their offer, but we are willing to negotiate. They got the message and the counter was a good one.
The response of, we are not going to respond, just leaves me at a loss. Does the Seller really want to sell? Will she only sell at list price and no other? Inquiring minds want to know! But at this rate we may never know. Its too bad really. The home is nice and I am sure that will a little give and take from both sides we could have made everyone moderately happy. By shutting down all communication, this seller is communicating that she is not interested in selling her home.