One of the prettiest sets!
Butterfly - $55-60 - tends to be the most sought after of the lot along with Diary and Shell I think
Candy - $35
Diary - $60
Heart - $40
Love - its all going to depend how pink her hair is, she is practically impossible to find it original so its almost always some degree of fading - $50-55
Shell - again up their with Diary and Butterfly for popularity and I think she also comes up for sale the least - $65-70
Singalong - again depending on her hair - assuming not completely faded $50
Star - $40 - she is not the most popular but oddly she, like Shell, seems to pop up the least often
I hope you manage to track them down
And keep an eye out on Euro ebays - they are your best bet for a bargain as often all of these ponies sell lower there than on collectors sites or ebay.com