Historical clue formulations

• Going rate? — 2020-08-30
• Soaring expense? — 2016-08-06
• Soaring cost? — 2015-12-27
• Delta factor? — 2013-02-01
• Expedia calculation — 2011-09-06
• United charge — 2009-11-08
• Expense report item — 2006-10-08
• Highflier's need — 2000-05-12
• American charge — 1999-01-06