Add cost estimation

### What would you like to be added?

We should provide a blurb saying how much the lab environment costs to run, something like:

> Cost to complete: This workshop will cost you less than $XX for 3 hours.*
>
> *This estimate assumes you follow the recommended configurations throughout the tutorial and terminate all resources immediately after you complete the tutorial.

### Why is this needed?

Users should know the expense of the Terraform they are deploying ahead of time.

Start by locating the workshop tutorial documentation and the Terraform configurations that define its recommended lab resources. Review the deployed resources and AWS pricing inputs, then document a cost estimate with the stated three-hour and immediate-termination assumptions.

Written by the indexing model from the issue text.