Study on EAP/OAP can be comparable to the cost of study at UC. In some cases, it is less. EAP participants pay UC fees and continue to receive UC financial aid while abroad. Furthermore, EAP students are eligible for special grants and scholarships from UC, the host country, and other sources.
OAP students may retain all or some of their funding while abroad, including special study abroad scholarships, but because of the variety of the programs found through OAP, costs for individual programs can vary greatly.
Check here for specific information about scholarships and financial aid: http://programsabroad.ucsd.edu/pao/funding.htm