US Customs is not involved in any premium charges made by any surety to a customer. US Customs administrates and collects the financial obligations for imports.

This is a charge made by the surety to the company that is the assigned payor for charges for each bond. The insurance company establishes the charges for any bond based on many risk items. For example, the surety charges more for a $100,000 bond than for a $50,000 bond.

They also charge additional for a bond with anti-dumping entries or a reconciliation rider, Periodical Monthly Statement, or for a warehouse bond, etc.

Basically, the insurance company charges a standard fee for standard exposures to loss.  They add surcharges for those particular risks with additional exposures and do not make all bond holders pay extra to cover these exposures which only a few have.

Another insurance example:  Insurance companies charge extra for home insurance in the brush area that has more exposure to fire loss or for earthquake insurance in high-risks zones. They also charge more for auto insurance if there is a young driver in the household, etc.