This is a tricky question
We work on hourly bases. It is normal, that projects keep changing during development and if a fixed price is provided, it may be sometimes quite difficult to work on the project.
Everybody ask for estimation, but it depends on many factors (e.g. Stackup, VIAs vs uVIAs, Size of board, Number and size of BGA components, Number of components, Number of pins, ... ) and it is sometimes very difficult to answer. Generally, simple boards are up to 50 hours, more complex boards (with a CPU and memory) starts around 200 hours.
Some time ago I have posted our timesheets from some projects, this may help you:
- How long it takes to design a Baseboard for Computer on Module
- How long it takes a Junior Engineer to design an Advanced board?
- x86 Custom Board Design â€“ How long it takes?
- How long Schematic design and PCB layout take â€“ Check here