I didn't go because it would have cost the guts of €50 to bring the family and I got the impression that most of the stands were selling stuff (I don't pay to enter the supermarket either). I have no idea whether it's economical to provide free entry to a show like this, neither do I particularly care.
On a venue-related note, I've avoided going to the RDS in the last year or so because my experience in the few years prior was that everything hosted there was overcrowded, overpriced and disappointing, and access is usually difficult with inadequate parking capacity. It's been rip-off Ireland distilled.
This isn't a criticism btw, I'm just explaining why I didn't go.