Am i obliged to buy when seller refused at first..

Audiogon expects users to know the rules and John (Jmcgrogan2) is correct, the offer is in effect until the seller declines. My first thought was that the seller's email declining the sale, and subsequent failure to "officially" decline the offer, could have been an attempt to drive up the buyer's original offer. However, a search of the seller shows he has been around here for 15 years (since 2000) and has maintained all positive feedback. Also, the neutral (originally negative) feedback message alleges the buyer failed to respond to emails. Given the buyer also has/had all positive feedback going back 5 years, I would have to see the email communication on both sides to form an opinion. If the seller's email to buyer declining the sale does in fact exist, a pass would have seemed a reasonable outcome.

Based on the rules/policies that govern trading at this site, when a prospective buyer makes an offer to purchase an item, the seller can select one of three actions pertaining to that offer,
1. Accept,
2. Decline, or
3. Counter.
Selecting one of these three actions triggers a specific outcome. However, the actions must be selected by using the tabs shown on the listing page, as there are no provisions for actions to be triggered by sending a message to the prospective buyer. In the event the seller does not select an action, then the offer expires after 48 hours. In this case, if the seller did not specifically select the action to "decline" the offer then, based on the buy/sell rules of this site, the offer would have remained active for 48 hours, during which time the seller could have still accepted the offer. The message discussed by the OP is not an accepted mechanism to decline the offer, based on the posted site buy/sell rules.

I agree with most here that, assuming the OP’s story is factual, then the seller displayed incredibly poor form. However, it may be good to remember we have not seen the message from the seller, or heard both sides. At a minimum, this situation is a good reminder of the importance of knowing the rules, which can be found by selecting "sell" at the bottom of the homepage. Unfortunately, you will need to follow a couple of additional links to see all of the information.