Scenario 1
Let’s compare m7i-flex.large and t4g.large with Unlimited mode enabled while CPU usage fluctuates over five days. Note that t4g.large can earn 36 CPU credits per hour, and the maximum earned credits that can be accrued is 864.

The instance is initialized and for the first 6-hour period remains idle, so CPU utilization is 0%. In that time, 216 credits are earned.
The CPU usage for the next 3 hours increases to 60%. That uses half of your CPU credits, leaving you with a balance of 108 credits.
For the next 6 hours, CPU utilization stays at 25%. 36 credits are earned. The balance is 144.
Next, CPU utilization stays at 40% for 18 hours, using 216 credits. The credit balance is -72.
For 12 hours, CPU utilization is at 30%. You neither gain nor lose credits.
The CPU usage for the next 18 hours increases to 80%. That uses 1080 credits putting the balance to -1152.
For the next 6 hours, CPU utilization stays at 25%. 36 credits are earned. The balance is now -1116.
CPU usage goes back up to 55% for 24 hours. 720 credits are used. The balance is -1836.
For 15 hours, CPU use is 75%. 630 credits are used and the balance is -2466.
Finally, for 12 hours before the instance is stopped, the CPU uses 60%. 432 credits are used for a total of -2898 credits.
The CPU surplus credits charged is 2898, which corresponds to 48.3 vCPU-hours. From there, we can calculate the total cost:

48.3 vCPU-hours * $0.04 * 2 CPUs = $3.86

The charge for the 120 hours of the On-Demand hourly rate is:

$0.0672 * 120 hours = $8.07

So the total cost is $11.928 for t4g.large.

m7i-flex.large is much simpler to calculate:

$0.09576 * 120 hours = $11.49

m7i-flex.large provides a 4% savings in this case.