Economical options for occasionally running massively parallel tasks

Use case: running a few massively parallel processes 1-2 times a month for 2-3 days each time.

What are the some of the most economical options? By economical, I mean monetary cost.

Will I require a reconfiguration each time I spin up this VM to run processes? Maybe this is related to persistent storage? The thing is, I would like to avoid having to spend 1hr setting up the environment everytime I want to logon for say 48 hours just to run a script...