Farnell Nederland is quoting me €1.06 (+21% VAT) for
the cheapest brand of
555 in stock. Their search won't let me find the cheapest microcontroller
without drilling down further, but an 8 pin AVR is €0.88.
Just checked RS components which is the supplier I normally use.
Assuming I want a through-hole DIP device (not surface mount), I can
get a TI NE555 for 28.4p if I buy 50 at a time. That is not a large
quantity even for a hobbyist.