I am not sure that anyone who does not keep their own horses can really appreciate how much work they are. At home, and more so at shows. And sometimes it is not just the actual work, it is also the watching and being ready for anything.
One day shows are a huge energy drain for trainers. I haul my own, and have quit going to one day shows just because they are so much work for me with one horse, much less a trainer with a bunch of horses. I am exhausted before the show even starts.
I completely agree with those who say if you want to avoid day fees, try the “meet at the gate” approach. You will soon realize that list of things that your trainer provides is endless. The getting up early to feed, the night checks, the use a of wheelbarrow or hose, the use of anything else you might have forgotten, the peace of mind knowing someone is at the show for long hours keeping an eye on your horse. I had a trainer once call me quite late at night to tell me my horse did not look quite right. She had stayed late to watch over him. I drove back out to the show grounds and he ended up fine, but her attention made me decide then and there that I was never going to complain about day fees.