Don't take this the wrong way.
But......
If the prices were not sky high (due to people paying stupid amounts for parts that are rare) this would not happen as much.
As an example you don't get mugged for a £7.99 Casio watch, but a £7000 Rolex is a bit different.
You won't stop it while there is a market for the parts.
Look at the recent theft and tracked to a pikey site, and the Police did not recover it.