Lambda is a decent choice when you need fast, spiky scaling for a lot simple self-contained tasks. It is a bad choice for heavy tasks like transcoding long videos, training a model, data analysis, and other compute-heavy tasks.
It's almost exactly the same price as EC2. What you don't get to control is the mix of vCPU and RAM. Lambda ties those two together. For equivalent EC2 instances the cost difference is astronomically small, on the order of pennies per month.
> like transcoding long videos, [...] data analysis, and other compute-heavy tasks
If you aren't breaking these up into multiple smaller independent segments then I would suggest that you're doing this wrong in the first place.
> training a model
You're going to want more than what a basic EC2 instance affords you in this case. The scaling factors and velocity are far less of a factor.
Care to elaborate?
https://medium.com/life-at-apollo-division/compare-the-cost-...
It should be obvious that this is not the best answer for all projects.