This is a search for a one-way flight from Salt Lake City to Sacramento on Friday, June 6, 2014. There are four non-stop flights on the route, although I'm showing only two of them in the screenshot, and all four of them are $500 for the one-way flight.
Now, examine the next screenshot, which depicts a search for a roundtrip flight on the same route:
The flights on the outbound portion of the roundtrip itinerary are precisely the same flights that are shown in the one-way search above, but, by flying rountrip, these flights are $126 cheaper than the one-way.
The lesson here is obvious: If you need to fly one-way on this date, buy a roundtrip ticket and throw away the return portion of the trip. You'll get your one-way trip for $374 instead of $500.
