The only issue would be having an approprate CAD drawing, as a one off laser cut job in 1/32 ply I would have thought it would come out between £10-15, our complete Midland signal box kits in 10mm scale start at only just over £100 Your quite right about mainstream etched brass, it would be killed on price by the cost of the photo tool, but there are other ways, a single sided etch produced using the laser to cut through a mask can produce a great scratch building aid (you would still need to cut the outline) or for a simple etch like the lower parts of the box home electronic type pcb etching methods can be used with great effect.
Andy Mould
Woodbury Models