Plan review fee
A separate charge for checking the drawings against code, commonly a percentage of the permit fee.
The building department, sometimes a third-party reviewer
Resubmittals after a rejection are frequently billed again. Two rounds of corrections can cost more than the original review.
Plan review is commonly set as a percentage of the building permit fee, often in the range of half to two-thirds, though this is entirely local.
Third-party review is increasingly common where departments are backlogged. It is usually faster and usually more expensive, and it is sometimes optional, which makes it a schedule-versus-cost decision worth asking about explicitly.
Expedited review programs exist in many jurisdictions for an additional fee. Whether that is worth it depends on your carry cost, which you know and the counter does not.