For commercial PCB layout expect to pay around £1.50p per pin.
It's a fantasy to assume you can send off a schematic and get a working PCB back. The PCB needs at least a basic specification, including:
Number of layers and stackup if required
Power plane allocation
Mechanical constraints – PCB size, position and size of mounting holes
Component location – especially for things like connectors
General signal flow – you don't want a thermocouple amplifier right next to a SMPS
Track width and gap – no point in having a 2A power supply coming out on an 8 thou track
Critical tracks such as high frequency lines, or high impedance which may require guarding
Any creepage and clearance requirements
And anything else!
None of the above is difficult, but needs doing or disaster results. As a warning, a company we have been working with commissioned a university to design a small optical particle counter for air quality measurement. The technician drew up the schematics and sent them off to a company for PCB layout and manufacture. When the boards came back they didn't do anything, except oscillate. Why? No decoupling capacitors on the high frequency opamps, doooh! They weren't on the schematic, as it was "obvious" you'd need them, but the PCB layout person didn't know anything about electronics and so didn't add them. Much money and time wasted.
Much has changed in the commercial world of PCB layout over the years, with many designs now being done in-house rather than farmed out. The PCB is as much a part of the circuit as the schematic and needs to be designed accordingly. I now do all my own PCB layout, unless the client dictates otherwise. That way I get what I want and can take into account all the mechanical and electrical constraints. Generally the boards work first time, which they often didn't in the good old, bad old, days of farming out the layout.
Good luck in finding someone to do the layout.
Andrew