The idea of a Bicentennial Quarter being worth nearly $90 million or others valued at over $50 million is extremely unlikely and not consistent with known values in the numismatic world.
The most expensive coins ever sold at auction are in the range of several million dollars, but these are typically coins with extraordinary historical significance and rarity, such as the 1794 Flowing Hair Dollar or the 1933 Double Eagle.
The Bicentennial Quarters were minted in large quantities. Even the special collector's edition silver quarters were produced in millions. High production numbers typically keep the value of a coin relatively low, as rarity is a key factor in a coin's value.
Most Bicentennial Quarters, unless they are in exceptional condition (like uncirculated or proof condition) or are part of a special mint set, are worth only a small premium over their face value.
A coin's value can be affected by several factors, including rarity, demand, condition, and historical significance, but achieving the valuations mentioned would be unprecedented for Bicentennial Quarters.
A valuation as high as tens of millions of dollars for a Bicentennial Quarter would represent an extreme outlier, unlike anything observed in the history of numismatics.
Such figures are far beyond the known market values for even the rarest and most unique coins. For accurate valuations, it is always advisable to consult with a reputable coin dealer or a numismatic expert.