Divide any quote by the market hourly rate and the picture clarifies immediately. A thousand a month where senior time costs a hundred buys ten hours — barely enough for reporting, a call and one content brief, let alone technical work and outreach. Retainers below roughly fifteen hours a month always drop a workstream; the honest ones say which.
Retainers suit continuous work: content, links, monitoring, and the endless small corrections a live site generates. Known, bounded problems — a migration, an audit, a template rebuild — are better bought as projects with a defined deliverable. Many good engagements start as a project and become a retainer once the backlog is clear.