Apple loves products with a very high profit margin. Automakers survive on much smaller profit margins (negative margins with regards to certain economy and hybrid models) and experience losses from time to time. If Apple wants to burn through their cash quickly this would be a good way. Engineering is only a small part of the expense. Building a factory (unless they will import the car from China which is possible) building a dealer network, supplier contracts, marketing, safety standards and testing, etc...
It would take billions getting into this business and then they still have to compete against GM, Ford, Toyota, Fiat-Chrysler, Nissan-Renault, etc. who have been established in this business for many years. For example Ford is 112 years old. It is a very saturated market and at least in the United States if you want to actually make profit you better be ready to release some luxury cars, trucks and SUVs.
If they want to do as a hobby to blow through some cash I guess that is their decision, but if they think everyone will line up to fork over some outrageous price for an Apple car like an iPhone I think they will be severely disappointed.