After keeping tabs on Kayak for a one-way SEA to BOI off and on for a few weeks, with no signs of flux from a pretty horrific (to me) $800 for 3 day rental, booked rez with Hertz (carrying lowest fare- don't rent enough to have loyalty). Then realized I should have made it for compact, not economy. Cancelled rez, back to Kayak and suddenly there's a Thrifty one-way for about half what i'd been seeing.

I grabbed it of course. This morning Kayak is showing prices back up where they were. The flux was mainly in the drop fee (from $500 to $223) but the others were slightly lower too, I assume calculated as a percentage ala taxes.

Was this a freak thing or is that kind of flux common?