Do we ever find out what happened to Chrollo?
Chrollo successfully had his chain removed by the Greed Island Exorcist. 

He doesn't need to pay a price except whatever he paid to hire the exorcist to help him. Gon only lost his Nen because he violated a Contract, and even then it isn't confirmed that he is completely nen free. 

Chrollo can still wield his book, and he used so very efficiently when fighting with Hisoka.