Depends on the wave, condition and if the pony comes with a card or not. Loose without card ponies from newer waves are 1-2$. Together with cards they can go for 3-4$. Rare ponies like Princess Twilight Sparkle, Princess Luna/Celestia/Cadance, ponies from sets, Fluttershy on her own mold and pretty much any pony with an original unique mold are 5-10$ with cards. Same for wave 2 ponies - they're Europe only exclusive.