If you try to get things perfect the first time you'll never ship on time.
Doing the right things in the right order usually involves optimizing different constraints at the start and re-balancing your optimizations as you prove your product idea, learn what you don't yet know, and gain additional resources and time.
Don’t get the 27” inch iMac, get a second hand office chair. This will free up enough cash so you can take the more expensive but quicker hosting / infra options like Heroku and Lambda.
There is a reason Amazon gives away a lot of free credits to startups, and it's the same reason drug dealers give away free samples. If the economics are right, and growth is strong then you might be okay - but you also don't want to find yourself with a $100k/month AWS bill in a startup with only $2m of annual revenue.
(P.S Greetings from the other side of the Spree. I love La Lucha on your street!)
If using FaaS can be a quick bandaid solution to get you up and running without worrying about having to design your own equivalent of the fail whale, then a certain degree of lock-in might be worth paying.
FAAS (Or, MSA) adds a ton of complexity right off the bat. Why take on that risk when you have little money and less time?
I wonder if the fact that application load balancer can now invoke lambda functions could've made serverless viable. https://aws.amazon.com/about-aws/whats-new/2018/11/alb-can-n...
Mind you, the post was written in August 2018 and the above announcement was made in December 2018.
And it's fairly trivial to set up autoscaling distributed Elixir on Google's Kubernetes offering.
You can start with serverless, move to normal cloud instances and finally to bare metal or the other way around!
For example, the core value provided by an ERP software is not performance but the business logic. Serverless is a good fit for startups creating such software. If you are running a conference call business or serving tons of video like Netflix, a different architecture better suits your need. Such as having edge servers with every ISP.