[ManishR]

Disclosure: I work for AWS and am part of the team that built EC2 Mac instances

The 24 hours minimum is applicable to the allocation duration a Mac1 Dedicated Host, and not to the instances running on that host. Put differently - once allocated, a Mac1 Dedicated Host can only be released from your account after 24 hours. You can however can launch, stop, start, and terminate as many mac1.metal instances with fresh macOS AMIs on that host as you need while that host remains allocated to you.

Additionally, Savings Plan (https://aws.amazon.com/savingsplans/) on Mac1 instances can provide up to 44% savings over On-demand prices for longer term commitments.

[gregmac]

Ok that sounds promising. I haven't really used dedicated instances so I'll have a closer look at this. Thanks!