How to deal with pit fighting? [closed]

A player in a game I run tries to do pit fighting in every city they visit. The pit fighting rules from XGtE require a week, so at first I considered a version of that with less gold at the end. But it seems quite easy to win at those, and that player quickly got much more gold than everyone else. Also, rolling three times seems quite a bit ing way to run a fight.
Mh question is this: how can I make pit fighting more interesting and challenging, shorts of doing an entire combat?