About the Z80 pricing, in 1981 I was able to buy a Z80A and two PIO chips for $3 each in Brazil (lots of taxes). Some of the larger TTL chips (like bidirectiona

About the Z80 pricing, in 1981 I was able to buy a Z80A and two PIO chips for $3 each in Brazil (lots of taxes). Some of the larger TTL chips (like bidirectional buffers) cost more than that, so when a group asked me to design a CP/M computer in 1984 I actually added extra Z80s (to generate video and for the two GPIB interfaces) to save TTLs.