Maybe, but much more expensive to start with a large billet I'd guess.
There are some neat casting process' that involve making a part from the hard foam that you buy at home depot to insulate with, it's polypropylene,I believe, is usually blue, or pink, and it can be used to make casting forms out of. It sands very well, but is irritating to work with; eye protection required.
Once you have a correct form carved, or machined, allowing for the shrinkage of aluminum(1/4" per foot I believe), you have the foundry pack sand around the form, in a box with a hole on top to add the molten aluminum.
I have a foundry near my house, and have thought about how easy it could be to creat a new base for some ITBs, or a slightly different process for some camshaft blanks.
A co-worker has been doing basic sand casting of tether car models for years, an obscure, collector hobby shared by a handful of mostly older enthusiasts. The models are flawless when completed, and sell for several thousand dollars, by word of mouth, interesting I thought.