The honest answer depends less on complexity than on method. The same need can take two weeks or eighteen months depending on how you cut the work.
Why projects drag on
On the traditional market, you often count in months, sometimes years. The cause is not the technology. It is the scope inflated from the start, the layers of spec documents, the cascading sign-offs, and the urge to ship everything at once. The bigger the project, the longer, costlier, and riskier it gets.
Two weeks per brick
At 5000.dev, a working brick ships in two weeks. Those two weeks cover only the development. All the understanding work, the business, the constraints, the mockups of every screen, happens before kickoff. That preparation is what makes two weeks possible, not a team sprinting at nothing.
What fits in a brick
A brick is not a full software. It is the piece that holds the most value today, delivered, live, usable. A full software is cut into several bricks shipped one after another, each learning from the last with a real tool in hand.
For the full method, see our pages on custom software and the custom web application.