Anybody with enough money could enter Helios's nightclub. The day club, however, was an exclusive playground where only invitees and top-level customers could attend. It was often used by young businessmen to talk about serious matters or treat sophisticated business partners with quality wine, whisky, and cigars.
People trying to climb the social ladder would never refuse an offer to come to Helios's day club. That alone was enough to brag about in their office, or within their circle of acquaintance. An excellent conversation opener while trying to pick someone up.
Naturally, Ethan wouldn't refuse Sarah's invitation to go there, even if he had to sacrifice an office worker's precious weekend.