They are popular with bangs - but its not always people are willing to pay more for a pony you can get cheaper (just minus the bangs elsewhere). Its very much about who is looking at at the time - hence why you may get no interest one place and then $40 somewhere else.
MIB Rainbow Dash with bangs - $12
MIB Daisy Dreams with bangs - $22-24
But from Sea Breezes experience you may be better of auctioning Daisy with a reserve on ebay perhaps?