Manchester United's valuation on the New York Stock Exchange plummeted by more than £500m (€585.8m) in the wake of a report that the Glazers have decided not to sell.Nine months ago the owners announced a full sale was among the options being considered as part of a strategic review at the Old Trafford club.Sheikh Jassim and Jim Ratcliffe made offers to buy United, yet the interminable potential takeover process rumbles on as fans continue to protest against the Glazers.Hopes of a full sale were seemingly dashed when the Mail on Sunday reported that the owners are taking the club off the market and will try to sell again in 2025.That report led to more than £500m (€585.8m)being knocked off United's share price on Tuesday.After the New York Stock Exchange reopened following the Labor Day holiday, the price plummeted from 23.66 (€22) to 19.35 (€22.67) by close.United's market capitalisation - the company's worth on the stock market - was left at 3.15billion (€2.9billion) after the 18.22% drop.Earlier this year the Glazer family reportedly valued United at €7bn.