Whoah!!
Two different models, not related to payscales fundamentally.
High cost is interline bags and passengers between airlines, and have a res system and baggage handling system which supports that.
Low cost is point to point trips. We don't know, or want to know, about whatever on-carriage arrangements you might have. We have a (cheaper) res system and baggage handling system which supports that.
Big biccies right there.