Those are working for paypal but only for spending money,you can't verify your account and they work great in online shops.
You get them for free but you need a lot of US phone numbers so I think that OP is spending money on those numbers and his asking price is ok.
~Hamuki - sorry for my pervious post but I got angry when you said that those can be used for verification.
I wasnt fully sure.. So no hard feelings
Im just looking for buyers
I also have 6$ amazon cards I can sell for 5$ if ya want xD