ML Training Models - Estimate cost

Amazon SageMaker makes it easy to train machine learning (ML) models by providing everything you need to train, tune, and debug models. You are charged for usage of the instance type you choose based on the duration of use.

Reference : https://aws.amazon.com/sagemaker/pricing/#On-Demand_Pricing

It depends but relatively small data set can be for example, less than 50–100 GB. See this blog https://aws.amazon.com/blogs/machine-learning/choose-the-best-data-source-for-your-amazon-sagemaker-training-job/ for Choose the best data source for your Amazon SageMaker training job.