Growth marketing agencies sell a method rather than a channel: experiments across acquisition, activation and retention, run in cycles, measured against one metric. The business hiring one should brief that metric in its own words, the cadence of experiments it expects, and the ownership of everything the experiments produce, then compare the retainer with a growth hire on the worksheet on this site; The U.S. Bureau of Labor Statistics, cited below, puts the median pay for market research analysts and marketing specialists at $78,760 in May 2025 and the median for advertising, promotions, and marketing managers at $165,780 per year in 2025.
Name the metric and its current value
Growth agencies move whatever metric is easiest to move; the brief names the one the business needs, its current value and the period. The scorecard scores each proposal on whether it commits to that metric with a cadence.
Brief the experiment cadence and the reporting
How many experiments a month, how they are prioritised, how results are reported and what happens to the losers: a growth retainer without a cadence is a marketing retainer with a new name. Retainvia Pro holds the cadence in the brief and records what ran.
Own the results and compare with a hire
Landing pages, tracking, creative and learnings belong to the business. A growth hire at the published medians against the retainer on the hours the cadence needs: the worksheet prints both, and the crossover usually depends on how many channels the experiments touch at once.
Questions people ask about growth marketing agencies
What is the difference between a growth marketing agency and a digital agency?
The method: experiments against one metric across the funnel, rather than channel management. Brief for the cadence and the metric.
What should a growth marketing agency cost?
The management fee for the hours the brief asks for, compared on the worksheet with the loaded cost of a hire; any media spend is your money and sits outside the fee.
How is Retainvia priced?
$49 a month for the business, with no per-user fee; the free in-house versus agency worksheet needs no account.