An interesting and important question. I agree a quick response might be interpreted as desperate to some, but to others it is simply the professional thing to do. Let's say there is a home listed but without a price. I contact the real estate agent to get a price, and he phones back with the information within the hour. Do I view that as desperate? Not me. Or I am interested in an automobile, but not the asking price. I submit an offer. While we all know that games are sometimes played, I would not view a quick response as desperate.
I guess my simple answer would be to view it from the perspective of expectations from other things a business might be buying that are in the same price class.
One danger of much delay, is that clearly the person who has made the offer has enthusiasm now for the name, which might wane if in waiting and continuing to browse the potential client finds other possibilities.
Bob