Chuck(G)
25k Member
The PIC16F628A costs about $2 in quantities of 1 and provides 16 GPIO pins (if you're willing to use HV programming only, internal oscillator, and no /RESET line) in an 18-pin package. The SOIC version isn't hard to solder by hand -- I've made several home-etched boards using the SMT PIC16F84 and an old Rat Shack 15 Watt iron.
The programming issue is the big thing on my mind--it's been a headache for Hargle and others. The ISP programming of the AVRs makes matters considerably simpler--and cheap USB AVR programmers are easy to come by, so just about anyone could do these.
One of the reasons I'd asked about any demand for using USB keyboards is that many USB-capable chips also have USB boot loader capabilities (e.g. AVR AT90USB) so that no special programmer is required at all. AFAIK, all are 3.3V SMT designs and there didn't seem to be much interest in USB capability.