I made an offer to a local seller based on a local online ad. No response. A followup indicating that my offer was negotiable depending on actual condition after viewing was sent. No response. I have seen ads stating the seller would not respond to low-ball offers. It is the seller's option to respond or not but IMO listing as 'best offer' implies that the item is truly for sale and offers are being gathered over a short period of time and the seller actually WANTS to sell the item and will sell to the best offer. At least respond to all contacts. Let's do business. If you are just testing the market you are wasting my time.