Which AWS service will allow a user to set custom cost and usage limits, and...

 AWS Budgets allows you to set custom budgets that alert you when your costs or usage exceed (or are forecasted to exceed) your budgeted amount. You can also use AWS Budgets to set reservation utilization or coverage targets and receive alerts when your utilization drops below the threshold you define. AWS Budgets provides you with a comprehensive view of your cost and usage, as well as your reservation utilization and coverage1.