Concorde fallacy
noun [ S ]
ECONOMICS, MANAGEMENT ukusthe idea that you should continue to spend money on a project, product, etc. in order not to waste the money or effort you have already put into it, which may lead to bad decisions:
The Concorde fallacy refers to the fact that the British and French governments continued to fund the aircraft even after it became apparent there was no longer an economic case for it.
Compare
sunk cost