Yes, most of the hard work is done for you but........
The $2100 5.7 GM crate motor comes with you having to install the pan, the valve covers, the intake manifold and fuel injectors, the throttle body and the water pump. By the time you finish doing all that, you are going to be approaching $3K anyway.
Then there is the matter of some personal satisfaction every time I turn the key.
Kinda like every time I push the on button on this computer. (g)