Do you love it? Do you want to have ten or twenty or one hundred of them all over your house? Would you miss it terribly if it disappeared? Would you prefer to play with it and pose it on your furniture next to your emo bear rather than humanely release it for the iMG profit??
I adore the squids, the fireflies and the firebog street vendor, none of which are very rare or pricey. They have a high value in my mind.
If you don't love it like crazy, then the above link really helps to find a good price to sell at without gouging the customers.