i think most importantly their forumlats are different
love bud is a lustre as well as gleam and say,yeah is a veluxe pearl
im not sure about expensive pink though
i only have gleam and say yeah... color wise gleam seems more of a pastel pink and say yeah has more copper/gold highlights on me
Expensive Pink is also a veluxe pearl and is deeper and more pink than the others. I saw Love Bud last week and i'd have to say it is quite alot brighter and less pink than Expensive Pink, not as gold as Say, Yeah and not as coarse as Gleam and it also has more colour value to it too.