I'm told 65XX cores were used as the basis for several hard drive controllers of the era
Western Design Center is still (apparently) making a profit at least in part licensing 6502 core IP for embedded stuff. There's probably a 6502 buried and unrecognized in all sorts of low-cost control applications laying around you.
RC5 on an 8085
Oof. Well played.
65C02s are $8 now. That didn't stop me buying one when I was stuck at home during COVID. And a 6809 too.
But forget AVR. Yeah, for a buck or so the ATTiny85 was my go-to small MCU five years ago, and the $5 328 for bigger tasks.
But for the last three years both can be replaced by a 48 MHz 32 bit RISC-V CH32V003 for $0.10 for the 8 pin package (like ATTiny85, and also no external components needed) and $0.20 for the 20 pin package with basically the same number of GPIOs as the 328. At 2k RAM and 16K flash it's the same RAM and a little less flash than the ATMega328 -- but not as much as you'd think as RISC-V handles 16 and 32 bit values and pointers sooo much better.
And now you have the CH32V002/4/5/6 with enhanced CPU and more RAM and/or flash -- up to 8K rAM and 62K flash on the 006 -- and still for around the $0.10-$0.20 price
There are uC versions like the W65C134S: https://www.westerndesigncenter.com/wdc/w65c134s-chip.php
I dunno. The 6502 has been a $2 part for a long time but needs RAM and some glue logic, for a similar price you can get an AVR-8 [1] or ESP-32 [2] and get some RAM and GPIO.
[1] faster, more registers than the IBM 360, << 64k RAM
[2] much faster, 32bit, >> 64k RAM