The repeat releases on them all - even if slightly different and different packaging - means a lot of them are not that expensive. Pinkie probably suffers the worst.
Pinkie Pie - retail
Rainbow Dash - retail
Rarity - retail
Fluttershy - $20
Twilight Sparkle - retail
Applejack - she does remain the exception to the rule despite her second release (probably to do with the bangs on the first release, the fact she has only been released twice and also I think she has become a "got to have" kind of release) - she is not a $250 pony any more but I would still put her at the $130-140 mark MIB
MIB - original Fashion Style releases