When it comes to the Airport Lounge Access for diamond tier users - strictly speaking for European Trip.com accounts here - it makes a difference which country/language you chose in your profile. Some countries/languages might offer the flight for one or two USD less, but then the Airport Lounge Access for free does not show up.

Same with many other promotions like Air China and China Eastern intra China flights for free if you book the international leg via Trip.com etc.

With the "more expensive countries" (if one can call them like this) the Airport Lounge Access perk basically appears almost every single time one tries to book a flight.

The value of the Trip coins change on an almost daily basis.