A VPS is cheap, predictable, and fully yours but you assemble the ops; a managed PaaS is convenient but runs on their infrastructure with usage-based pricing and some lock-in.
Where DollarDeploy sits: the convenience of a PaaS on top of a VPS you own. You get the deploy experience and the ops (HTTPS, backups, logs, monitoring) without hand-building them, while keeping VPS economics and ownership.
The bottom line: you stop choosing between cheap-and-manual and easy-and-metered.
Go deeper: why buy a VPS instead of a cloud provider.