'Does Expedia price match?': How to use Expedia's 'Price Match Promise' to get the lowest fare

· Expedia offers a "Price Match Promise" for a sliding scale fee on selected flights. 
· Expedia automatically checks for lower fares across airlines and allows customers to initiate their own checks.  
· If a lower fare is found between the time you purchased your airfare and the date of your trip, Expedia will refund...