I was wondering if it'd be possible to go further, and actually use it as a fully fledged keyboard, but with your choice of switches and mechanical layout... and turns out that somebody has been doing that already! basically reverse-engineering the matrix and hooking up your own switches to the logic board. You get TouchID, pretty good BT performance and integration in the Apple ecosystem, good battery life, ... and all in a single device.
You mean the cost of EDA software directly (paying Synopsys/Cadence for the software used to design, verify, and synthesize your own chips)? Or the actual R&D cost to design the chip itself? Or paying for prepackaged IP blocks (major ones like CPU cores, or lesser ones like I/O)?
CAPsMAN is a royal PITA to set up. You have to manually add all the wifi channels, map each AP to the channels it'll use, and a lot of busywork. Once it's set up, though, it works fine, and lets you upgrade all devices from the manager, etc.