the dutches are not too hard to find and start at around $40 or so, you can get good deals if you keep your eyes open
i would say baby dolphin, baby cat with colour change hair and baby flower are the most pricey at around $50-$60 each.
mexican starflower has just two versions, each has slightly different coloured hair
one has pastel colours and the other bright colour
i would say $20-$30 depending on condition.
both are in the nirvana gallery
http://mlparena.com/gallery2/main.php?g2_view=core.ShowItem&g2_itemId=347611&g2_page=2love pkw xxx