Spirit Airlines is a low cost, no frills carrier so if you're only concern about a cheap, short flight to a destination, with one personal bag that fits under your small seat, this is it.
They have a roundtrip airfare to/from Seattle (SEA) and Los Angeles (LAX) for $70, including taxes/fees.
Date availability: end of October through first two weeks of November, then again the first two weeks of December. There's also a couple of random dates the last week of January.
Check date availability on Google Flights and use those dates to book on Orbitz
Please note that while this fare is valid at time of posting, fares can fluctuate in a matter of minutes/hours/days.
My sample travel dates: Dec 2-5, 2016 (Weekend travel)