The schools being discussed in this thread (e.g. Cal Poly, San Diego State, Long Beach State) represent the California State University (CSU) system – not the University of California (UC) system. The majority of CCC transfer students move to the CSU system, which has larger enrollment, more campuses, lower tuition, and easier admissions standards than the UC system. Historically, pretty much any CCC grad could transfer into pretty much any CSU campus. That can no longer be taken for granted, as certain CSUs have become more selective.
The CSU system has the equivalent of TAG, called the Associate Degree for Transfer (ADT) program. However, the ADT program only guarantees admission into the CSU system as a whole, not to a specific campus. So you could be admitted to a campus hundreds of miles away – in fact, the more remote campuses are the most likely to have space.
The CSU system has traditionally stayed affordable through the simple approach of charging very low tuition – not by doling out large financial aid grants. So if you live at home rent-free and pay that low CSU tuition, you can get a very affordable education. But if you can’t get into your local CSU, and you have to pay for room and board elsewhere (which will likely exceed the tuition), then that strategy no longer works. Obviously the affordability will go down, and it’s unlikely that your CSU campus or the state will offer you a grant to make up the difference.