Tesla is operating at a loss, but Model S and Model X are sold at a high margin comparable to other cars in their category. Source: share holder letters.
They are selling cars at loss because of large capital investments in the future. If you look at R&D department of BMW, it won't be profitable, but it has rest of the established business of BMW to support it. Tesla now is a large R&D department, which waits for rest of the company to grow up.
Tesla would be profitable if it just sold the Model S. Its burning through cash because of R+D and capital expenditure. e.g. building the biggest factory in the world in order to make batteries cheaper.
It is possible that other branches of the business could subsidize car sales indefinitely, but highly unlikely.