Update: Also $85 round trip flights between Miami and Phoenix.
United has some super cheap dates between Charlotte and Las Vegas scattered in late May, June, and July at just $83 round trip in either direction (one stop at IAH – Houston). This sale is unlikely to drag out for long. If interested, head over to Google Flights now. Note that you may have to click on the departure date first to see the $83 prices (I’m seeing several dates that say $200-$300 until you click on the departure day, then you can see $83 return dates, so check different dates).
Remember that most United flights earn 100% mileage flown when credited to Singapore Airlines. According to the Great Circle Mapper, this round trip should be more than 4,200 miles.
If you book through an OTA, you should have 24 hours to cancel — so book first and check schedules later if interested.