Hi,
Its less than 10 dollars to build a standalone, maybe as low as seven dollars.
Heres one in a robot -
and one in a lap timer
For programming standalone setups I find this very useful -
http://www.oomlout.co.uk/usb-serial-converter-p-266.html
If you see the six pins in the bottom left of the laptimer circuit, this is a programming header that allows me to update the standalone Arduino software from the computer using the converter in the link above.
If you start with an UNO, its a pretty easy and well documented migration path to standalone Arduinos.
Duane B