It is very obvious that sex work involves money and is principally a trade of flesh. It is very far from two persons, straight or gay, involved in a love relationship, filled with commitment, desire and sacrifice through sickness and health.
Bestiality is sex with animals and does not involve consent. Sex between two consenting adults is also very far from the molestation of animals. It is perhaps because we understand conventional heterosexual relationships to be about men “taking” women that we think that bestiality could be the same as consensual relationship with human beings. But ideal sexual relationships between consenting adults involve full consent of both partners, so that no one is “taking” anyone like a man might take an animal or animals take each other.
Incest does not involve consent either. It usually involves emotional blackmail, power and control, bringing disharmony to the family unit rather than forging a tight between people so that a family unit can be formed.