The Red Arrows are only in existence to remind the British Public that the RAF still exists - if they go there will be next to no coverage and the"man in the Street" will forget all about them
It's not a cost/relevance issue - the moment they started using trainers (Gnats!) for display they became entertainment not a reflection of actual combat readiness
Look at the Royal Navy - they have effectively disappeared from public view........... except when the current Sec State needs a
PR puff