"Just use a VPS, it's cheaper" is true and also incomplete. The full comparison has three components: hosting cost, tooling cost, and your own time — and solo founders usually underprice that third one.
Hosting cost
Not close. A PaaS charges for convenience on top of raw compute; a VPS charges for the compute. For a small app, expect to pay 3-8x more on a PaaS for equivalent CPU/RAM once you price in the database, cache, and any add-ons.
Tooling cost
This is where "just use a VPS" quietly stops being free. Replicating what a PaaS gives you out of the box — build pipeline, HTTPS, zero-downtime deploys, database provisioning, backups, monitoring, log aggregation — either costs you in dollars (a deploy tool) or in hours (writing and maintaining your own scripts). Free and open-source tools exist, but "free" there means "your time," not "no cost."
Time cost — the one people forget to price
If you're a solo founder, an hour spent debugging a broken nginx config or a certbot renewal that silently failed is an hour not spent on the product. At almost any reasonable hourly value of your own time, a few hours a month of infrastructure fires costs more than the PaaS premium you were trying to avoid.
So which actually wins?
It depends entirely on whether the VPS route includes decent tooling. Bare VPS + manual scripts: cheapest in dollars, most expensive in time, and the most likely to have a 2am incident with no one to call. VPS + a deploy tool that handles provisioning/HTTPS/deploys/backups/monitoring: keeps the hosting cost advantage while removing most of the time cost. Full PaaS: most expensive in dollars, cheapest in time, zero infrastructure literacy required.
The practical takeaway
If you're technical enough to be comfortable with Docker and SSH but don't want to spend your weekends maintaining deploy scripts, "VPS + a deploy tool" is usually the actual optimum, not "VPS with nothing" or "PaaS forever." That's the specific gap DeployOS is built for — VPS economics with PaaS-level automation for provisioning, deploys, HTTPS, backups, and monitoring, as a one-time purchase rather than a recurring line item. Worth pricing out against your current Heroku/Render/Railway bill before renewing another year.