Source : Free On-Line Dictionary of Computing

break-even point
     
        In the process of implementing a new computer language, the
        point at which the language is sufficiently effective that one
        can implement the language in itself.  That is, for a new
        language called, hypothetically, FOOGOL, one has reached
        break-even when one can write a demonstration compiler for
        FOOGOL in FOOGOL, discard the original implementation
        language, and thereafter use working versions of FOOGOL to
        develop newer ones.  This is an important milestone.  See {My
        Favourite Toy Language}.
     
        [There actually is a language called {Foogol}].