The multiplier has not increased from 1/5 to 1/2. Off peak the multipliers about 1/4 today. It may have doubled or gone up 2.5x, but so have gas prices.  (eg, 50c to 1.10) 

Declining demand won't drve down prices (never mind the contradictory claim you've made there - nobody will drive them, but gas prices will drop since people are driving them?).  Producers will close the taps once it becomes unprofitable, which starts to happen at about $45/bbl, incidentally very near present prices.  OPEC can produce for less, but at $35 all their competition goes away so they can hold it there.