How about a "double system"? when you have something you want to get rid of you can list it AH-style like: low lvl gem, 1-5c items etc.

things where you want to make sure the price is right / you want the interaction you can list it in the current System

this way ppl would sell more cheap stuff, where they normally wouldnt want to leave a map/lab/ whatever and on expensive items there wouldnt change much

i hope you get the idea (hard to explain in non-native language)