It usually takes six people and as many handovers. A Product Engineer brings them together, so nothing gets lost between two trades.
What gets lost between two trades
Product, design, development, data, automation, AI: in a traditional project, each trade hands over to the next. At every handover, part of the intent disappears, and what you discover late is expensive to fix.
What it changes
One point of contact, from idea to production. Ten steps, and at each one a deliverable you can see, test or read: the brief, the prototype, the application, the data schema, the workflows. You talk to the person who builds, and a decision made in the morning can be live by evening.
What AI has changed
One person who thinks in product terms and knows how to use AI can now deliver what took a small team not so long ago. AI multiplies, it doesn't replace: understanding the problem, making choices and standing behind the quality of what you deliver can't be automated. That is where I spend my time.
When an agency is still the right choice
If your project needs several teams in parallel, an architecture for very high load, native mobile development or advanced security certifications, a larger organisation will be better placed. I'd rather tell you before we start. For a product, an automation or a business tool to put into service quickly, with one person responsible for the result, a Product Engineer is often the shortest route.