These are my own personal values, not necessarily what others might value these things.
GCs are worth around 9500 - 10000
Dreams Poster around 5k
Castle turret around 7.5k
I've seen ears go for 10 GCs
Rapunzel pin was 500 credits when buyable, so probably around 2k now, and same for Belle.
May want to seek a second opinion because I'm not great with values. Hope this gives you a good starting point