I know many people who spent major money on builds and most of them ran 5 times longer than quoted but on the flip side normally a small build turns into big builds and things keep changing as the build goes on.
Unless you've dropped big money on a build it's easy to say what you would and wouldn't have done. Truth is most all shops take time. You pull it out of one and put it into another you just back stuff up even longer. Keep in mind these are normally custom jobs not a basic kit install.
Built motor, turbo kit, custom parts to make turbo kit work correctly since it didn't, custom fuel lines, full fuel system, stand alone engine management, tuning...
Even my civic took 2 motors and 3 times as long as expected. Shit happens.
$40k ain't shit for a full build, especially for a lambo. I personally have friends, yes more than one who put more into their 350Zs.