It is almost impossible to hack whatsapp remotely.Notice the "almost"? If somebody can do this they won't be doing it for $150 dolar.Unless you have physcial access to device or you are on the same network with that device your chances are lower than zero.
I've seen some tutorials on google and youtube and that is worked, but the guy who shared the tutorial always hide the software he was using.
I know, for things like this will not be distributed freely and have to spend money to get that software or that service.
I'm sure hackers are everywhere even I'm sure hackers are also in this forum and they are always hiding, so if they see this thread I hope they contact me, I'm ready to pay more if he can prove the software will run well.