I applied to 8 and spent close to $1000 on applications, sending GRE scores, and transcripts. a lot of schools make you apply to the graduate school and not just through CDSCAS so that adds up. in hindsight I would have only applied to about 5. It's stressful to coordinate that many LORs, sending transcripts, and GRE scores because every school wants things sent in different places. not to mention interviewing at multiple schools can take its toll.