In-house
A marketing hire costs $70,000 to $110,000 fully loaded, and one person cannot be expert in search, social, streaming, creative, and analytics. The model works when your media budget is large enough that dedicated attention pays for itself — generally above $30,000 a month — or when marketing is so central to the business that it must live inside it.
Below that, you have bought a generalist and a lot of tabs.
Agency
An agency buys senior judgment, multi-discipline coverage, and someone accountable. It earns its fee when the strategic question is genuinely open, when you are entering a new market, or when brand work needs doing. Retainers of $3,000 to $15,000 a month make sense against media budgets several times that size.
The model breaks when the retainer approaches or exceeds the media budget, which is the situation most local businesses find themselves in.
Consolidated execution platform
You keep the decisions; a system plus a small team runs every channel. Costs are typically a small fraction of a retainer and do not scale punitively with spend. It works when you know your offer, want speed, and need coverage across channels you cannot staff for.
It is the wrong answer if what you actually need is someone to tell you what your marketing should say.
A rough decision rule
Under $2,000 a month in media: execution platform, no question — a retainer would eat everything. From $2,000 to $30,000: execution platform for the running of it, plus occasional paid strategic help when a real question comes up. Above $30,000: build a small in-house team, and consider an agency for brand and creative.
The mistake is not choosing wrong. It is staying in a model you outgrew three years ago.
For the full side-by-side, with what each option costs, the skills it assumes and what it takes to switch, read in-house vs agency marketing: how a small business should choose.