This is working as designed and is due to there not being a rate in the NBI_PROJ_RES_RATES_AND_COSTS for the resource and project combination. A rate must exist in the NBI_PROJ_RES_RATES_AND_COSTS table prior to exporting the project to MSP so that the resource rate can be exported as well. Once rates are populated in this table and exported to MSP, MSP will reflect the correct rate and calculate the expected costs.
In order to populate the NBI_PROJ_RES_RATES_AND_COSTS table, the Rate Matrix Extraction job will need to run. Alternatively, the on-the-fly Rate Matrix setting can be enabled under Administration - Health Report - Application tab. This is a system wide setting. When the on-the-fly Rate Matrix setting is enabled, the rates will populate in the NBI_PROJ_RES_RATES_AND_COSTS table as soon as the resource is added to the team AND
Update Cost Totals is run from the Actions drop down menu on the Team tab.
IMPORTANT: Impact of enabling this on-the-fly setting: