you would think the mains issues would be with the app (10% cut being one), the real issue comes from the people using the app. they all want to low ball you. u listed an item less than half of its retail value at 9/10 condition and people will offer money u could find under a sofa... honestly why bother messaging someone if u do not even have the facilities to shop for second hand goods. honestly very sad they should have a feature for people to make offers through a system like ebay could cut down on the time wasters.
TLDR; Low balling Time wasters.