The AMCAS processing fee for the primary application is $170 and it includes one medical school designation. Each additional school designations are $40. Thus if you apply to 20 schools, the primary application alone costs $930. Then each school has a secondary application fee which ranges from $25-100. If you get an interview, you need to pay for each flight and the overnight accommodations. You should anticipate spending at least $3000 on the application process. Here is a valuable cost calculating resource on AAMC.