When the president activates National Guard troops—ordering governors to call up troops based in their states—by law the federal government is only required to pay 75% of the deployment costs in the troops' home state or territory.
The Trump Administration picked up the full tab for an initial deployment of troops to help respond to the coronavirus outbreak. As of August it pulled back full support for most states for the rest of 2020. Continuing 100% support was initially restricted to two states with major outbreaks, Texas and Florida, but has since been extended as well to Arizona, California and Connecticut. Governors, Democratic legislators and Joe Biden are all urging the administration to extend support to all states.