It is my opinion that a hot sauna is not the ideal environment for pheromones. It is backed up by research into ant behavior with pheromones in variable temperature conditions. It seems that the pheromones are volatile and high temperatures degrade the effect. Which makes sense because they are generated in body temperature conditions and then released into generally cooler environments.
In 3rd edition, I would call that a stress failure, which has deleterious effects on the opposite gender. That probably isn't detailed in 4th, but neither are hot tubs and saunas.
Pheromones and spells and all those gimmicks are great for back alley deals with on the spot decisions, but for a long term contract, both parties need to be on a level playing field. If you pull a stunt like pheromones or magic in one of those deals, you'll never make a deal outside of the back alley.