Yup the producer spends money...but till early 2016...2/4 producers of TPK were also the writers of TPK...that's the reason we got to hear some good dialogues till that time.
Yes the director just directs the scenes...but he/she is responsible for getting the best out of the actors...getting the best possible shots. And yeah it's the director who decides how a scene will be shot which makes a huge difference.
The writers just write the dialogues and screenplays according to the instructions of the creatives...but yes the way they write things also makes a huge difference.
And the CVs...well they are the ones who decide what is going to be shown in the show...the tracks, sequences...everything is planned by them. If the producer is concerned about the show then they keep giving their inputs to the CVs (this was not the case with TPK since 2016 as the producers got busy with their other shows)
And yeah even the channel gives their input and ultimately approves/disapproves everything planned by the CVs. But it depends from channel to channel and most importantly the relation between channel and producer. There are some channel jo apni marzi chalate hain and they force the PH and CVs to regularly make changes according to the channel's wish. And there are channels which completely let the PH and CVs do their own thing.