The Trading Post guidelines and requirements are listed in this thread -
https://www.audiocircle.com/index.php?topic=454.0Note "Individual for sale items must list an asking price." and
"BUMPS
1. Weekly bumps are permitted.
2. Changes in pricing are a permitted bump at anytime. No, one dollar reductions are not acceptable and will be considered a bump.
3. Violations will result in the whole thread moved to the waste bin.
If you need to bump your ad perhaps you should consider lowering your price."
There are also helpful suggestions in the thread linked. For example, location is one. Particularly if one is selling heavy speakers.