USPS real-time rates through Endicia is lower than what is calculated in USPS website because Endicia offers discounted Delivery Confirmation, Signature Confirmation® and low-cost insurance fee (http://www.usps.com/onlinepostage/welcome.htm).
Notes: The insurance quoted through the NetSuite integration is not the same as what is provided in the USPS website. The insurance is being provided by a third party (U-PIC), through USPS postage reseller Endicia. That’s why they charge lower insurance.