Should I hire an in-house marketing team or use an agency?
It depends almost entirely on budget scale and management capacity. An agency gives you several specialists part-time for a fixed fee, with no hiring risk and no idle capacity. An in-house team gives you dedicated attention: faster internal context and full control, but you carry salaries, tooling, training and turnover whether or not there is work that month. The crossover in India tends to sit around Rs 3,00,000 monthly total marketing spend.
The comparison is usually presented as retainer versus one salary, which is not the real comparison. Digital marketing is not one job. It is at least four distinct skill sets, paid media, SEO and content, creative production, and analytics and tracking, and they are rarely found in the same person at a level worth paying for.
So the honest version of this calculation asks what it costs to cover all four adequately, in-house, in India, including the costs that do not appear on the salary line.