In D.C. 2020, the Guard put the peak daily cost at ~$2.65M for ~5,000 troops, about $530 per Guard/day. That’s a decent order-of-magnitude yardstick for today. Source: Reuters (contemporaneous) – https://www.reuters.com/article/world/what-was-the-cost-for-the-national-guard-to-deploy-in-dc-up-to-26-million-a-idUSKBN23J05Y/
For a rough scale: 800–1,200 troops = mid–six figures per day, before you add transport/lodging decisions that move the number a lot. A recent LA activation was budgeted $134M for 60 days ($2.2M/day) off DoD testimony, which matches that ballpark.