ORGANISERS of the Hong Kong to Shenzhen Marathon will decide in four weeks time whether or not the event's $500,000 price tag is worth the effort. The event is in jeopardy with the Hong Kong Amateur Athletic Association being asked to pay a $500,000 administration fee to Shenzhen authorities. Officials said the association could not afford such an amount, which Shenzhen wanted to ensure proper ambulance, police and marshalling services for the Chinese New Year event. A spokesman for the association said yesterday: ''We probably won't be making a decision until mid-December.'' The two sides were originally scheduled to meet this week, but that has been put off until next month. A similar situation occurred at this year's event where the HKAAA suffered a massive loss after paying administrative fees of $280,000.