Returning to the module front panel and its cost for a moment, there might be some money to be saved by separating the slider faders from the rest of the panel so for example there would be a 4U high panel for faders and, say, 3U or 5U for the plug in module. A single panel holding all the faders will be significantly cheaper than a dozen or more individual fader panels. Normally I would avoid large panel like this because they can be a nightmare for servicing but as long as there is little more than a fader per channel this objection does not apply.
So, I have just designed a rough front panel with 13 faders and their legends on a 4U panel which is 105HP wide (13 x 8 = 104 which is a "standard width in the synth world). The cost comes out at 171 Euros which is basically 13 euros per fader. (fpd file attached using
@MidnightArrakis patent method of simply adding .pdf to the whole file name.
Cheers
Ian