Based on a cursory search, I could get a Postgres RDS instance with 250GB storage, 2 vCPU, 4GB memory for ~$80/month, but I'd have to spend $560/month to get that amount of storage on Digitalocean, and I'd end up with a ton of resources I don't need. The price difference on the database alone probably negates any money I would save from using Droplets over EC2 or Lightsail.

I don't know about everyone else, but I prefer Digitalocean over AWS because of it's UI/UX, predictable pricing, and because it's generally cheaper than AWS. #3 is unfortunately (as it often is) the most important of those reasons.

I really need this. Otherwise I will be forced to move somewhere else.

Yes, very required! I am using Lightsails just because they give more storage.