As far as I'm aware, it's a name only, I don't believe they were paid. The only difference is the level of money that's gone into making the tournament happen (hiring an exhibition space, a film crew, etc...)
Hm, surely it's rather pointless to call it 'professional' if only support staff get paid but not the players?
I obviously completely appreciate that these are all trials and that the polo cottage industry isn't that plush yet, but surely at least some kind of small pay for the players would be required to make the name genuine?
NB I actually have no opinion as to whether polo should try out professionalism or not.