Advertising is only a small portion of marketing. Probably 1/3rd of 1 persons job is spending that $3k media spend.

The rest of the team works on things like branding, identifying markets/customers, picking price points, running tables at events, writing content, working on the website, researching potential new products, understanding how current users use the products, analyzing web site traffic for insights, etc. At some places things like ui/ux fall under marketing - like making it easier for a user to purchase a product, writing manuals/user guides, etc.