> I didn't say it's cheaper for the same cache size.

So be specific. What exactly did you wanted to say?

> But yeah a base tier Redis that will carry a small project tends to be a lot cheaper than the base tier Postgres.

This is patently false. I mean,some cloud providers offer nosql databases with sub-20ms performance as part of their free tier.

Just go ahead and provide any evidence, any at all,that support the idea that Redis is cheaper than Postgres. Any concrete data will do.

Look at the Heroku pricing. If you don't like Heroku then look at AWS pricing. Specifically for Postgres, not a NoSQL DB (which Redis can be too)