There are a lot of factors that go into responding to this question. There are audit, consulting, software, internal resources, and other factors to consider which can easily grow from $30,000 to $200,000 depending on how the effort is accounted for.
What is SSAE 18 (formerly SSAE 16)?
The SSAE 18 audit standard is a framework for reporting on an examination of controls at a service organization relevant to user entities’ internal control over financial reporting.