The prices have been fluctuating wildly. In July when Hawaii started allowing fully vaccinated people to travel without testing, the prices were $500-$600 for economy. After the governor asked people to stop traveling to Hawaii I saw them fall to $200-$300.
Pre-covid, $500-$650 was normal for a non-stop flight on Hawaiian. $400 on Southwest. HNL-LAS is one of the most popular and underserved routes - they call Vegas the 9th island for a reason!