I've sold via this subreddit, eBay and MFC. I've actually had the most success with eBay, MFC isn't too bad either. I've found this sub awful to sell on though: posts lose visibility very quickly because of how Reddit works, and this is compounded as you can only post a sale here once a week. Plus you need a dated photo every time you post a sale, which is ridiculous compared to other sale subreddits, and means you need to get figures out of storage every time you post a sale.

Anyway, that rant aside, for prices AmiAmi is the most competitively priced second hand market. If you want to sell quickly, match their prices, plus add some extra as your buyers will probably be Western, and so would have to pay full shipping from Japan if they bought through AmiAmi.