Now if somebody from China can make a list of the cheap micros under 1-2 RMB, now that would be a nice list for super low cost stuff.. that I'd be very interested in...
I ended up ordering the Attiny13A as that was the cheapest option in aliexpress/ebay with freeshipping in small quantities (around USD $0.3 a piece).
I would have loved to find something even cheaper!
The STC8 and N76 parts are 8051, the other two are their own design. The HT-66 looks very much like a PIC16 part, and IDE and compiler are totally free.
The STM8 is probably the best-performing part in that price range, and has a free IDE and compiler.
My review includes pretty extensive discussion on the main page, plus separate reviews for all these parts — check it out and let me know if I need to clarify anything!
I made a repository for the toolchain necessary to get STM boards working here: https://github.com/abraithwaite/STM32
Although it's outdated, the links at the bottom appear to link to updated tools which are presumably better :-)