[anantzoid]

Spot instances cost way cheaper. The only downside is you need to create an AMI everytime before termination. But, also, AWS g2 has NVIDIA Grid K50 with 4GB memory, so it's not very good with performance.

[alien_]

The AMI creation is only needed if you store data on the machines, which you shouldn't do anyway, not even with on-demand ones.

You should always try to keep the instances stateless and store any data outside the instances, such as on S3 or EFS.