Amanda Staveley emerged as a prospective buyer for the Magpies late last year but, according to The Sun, the new price will deter the businesswoman.
Staveley and her equity company PCP Capital Partners were reportedly close to buying Newcastle for more than £300m before the talks with Ashley broke down.
According to the report, the revaluation has cast doubt on the possibility of Staveley tabling a fresh bid and raised questions about the future of Magpies manager Rafael Benitez.
The Spanish coach is said to have been banking on a successful takeover bid to provide him with a transfer warchest for next season.
Consequently, the former Liverpool boss could reportedly consider managerial opportunities elsewhere due to his budgetary restrictions at St James' Park.