I would not know where to start with a collectible market.
As for Flat rate boxes, I discovered those earlier this year, that was a good move. However, most of the items I sell are bigger than that (I sell mostly bedding supplies), so I cannot use them.
I just ordered a new batch of items - this time around I will keep track of everything to see if I am making a profit and how much. It will also enable me to see where I can make improvements and how I can incorporate fees so that they are not eating away at my profits.
