Any successful acquisition of easyJet by US investment firm Castlelake would carry a substantial ongoing financial burden: an estimated £1 billion in brand licensing fees to use the 'easy' name.
The cost stems from a royalty agreement between the airline and easyGroup, the holding company owned by easyJet founder Sir Stelios Haji-Ioannou.
Under the existing terms, easyJet pays easyGroup an annual royalty equal to 0.25% of the airline's total revenues.
This structure means that as the carrier's revenue base grows, so too does the annual payment to the founder's group.
For a potential buyer like Castlelake, this represents a fixed, recurring cost that would impact the post-acquisition cash flow and valuation of the business.
The revelation of this hidden cost comes as Castlelake attempts to secure a deal with the British low-cost carrier. easyJet's board has already rejected four takeover proposals from the US firm, most recently dismissing a £4.93 billion offer as insufficient.