What server architecture solutions do startups use?

I am a primarily Python developer who works with fairly larger clients. We use AWS as our main infrastructure for load-balancing, networking, app servers, celery/redis servers, Postgres on RDS, etc

For full blown Test/Stage & Scalable Prod deployments for even our small/med projects this is costing between $1-3k a month.

I'm curious how startups handle these costs. You can spin up a Digital Ocean droplet for ~$25, Heroku for something similar. Do people do this and just cram Django/Celery/Redis/Postgres/Node (or their equivalents) all on the same server and go with it?