Interestingly I found the online UA fare from HKG to EZE is only around US$2500 (including tax & charges) and believe that it is a H fare with stopovers allowed. It seems really cheap compared to the ex-US fares.

It is quite suitable for me since it is a side trip to my US business trip but the down side is the expectedly low seats availability when I fix up my itn in December for late January/early February travel.

Just keep my fingers crossed