If the intent of the 20-year patent protection is to allow inventor to recoup cost to develop the product, then require them to file with the patent application what that cost was.  Once that cost has been recouped, the patent can not be extended, and if the cumulative profit exceeds a certain multiple of the development cost, then the patent would expire, allowing in competitors.  This would allow inventors to recoup their cost and earn a fair profit from the invention but not allow an unjustified windfall.

If the intent of the 20-year patent protection is to allow inventor to recoup cost to develop the product, then require them to file with the patent application what that cost was.  Once that cost has been recouped, the patent can not be extended, and if the cumulative profit exceeds a certain multiple of the development cost, then the patent would expire, allowing in competitors.  This would allow inventors to recoup their cost and earn a fair profit from the invention but not allow an unjustified windfall.

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