You are completely missing the point. I'll try one last time.
A regular, professional caddie will get paid a small salary (that barely, if at all, covers expenses) and a share of earnings. That share will vary, both by player and by result. It will probably be in the range of 5-10%.
BUT to earn that money a regular, professional caddie will do some or all of the following - carry the bag, keep the clubs clean, keep the grips and player dry in the rain, learn the players game inside out so that they can provide advice on club and shot selection, discuss course strategy, help with yardages, read putts, know when the player needs to focus or relax (and know how to help them do that), overrule a player on shot selection, live out of a suitcase and follow the player around on tour... and probably a bunch of other things that I've either forgotten or don't know about.
Ortiz, who reportedly doesn't speak much English, would have been expected to do a fraction of what Kuchar's regular caddie does - basically carry the bag and not much more. That is why a regular caddie gets paid what they get paid, and why a random replacement does not.
So, if you are basing your view that Kuchar underpaid him on 'custom', I don't think you understand golf.
If you are basing it on the fact that Kuchar is already rich and doesn't need another $1.3m (less taxes, agents fees, etc), then that's a completely different argument. I disagree with it, but it's not a totally unreasonable conclusion.
And I don't think Kuchar is sorry at all. He gave his honest view when this first blew up. I'm also sure that plenty of players ageee with him, but none are going to risk the backlash from the media or uninformed 'fans'.