Steve Lusardi wrote:
$10 solution? I guess you don't build many things. How much is your time
worth? How much effort do you think it will take you to source the
apprpriate parts, even if you could? If you couldn't, do you have the tools
to make them? Material cost? Then you have the performance, accuracy,
liniarity, data display and verification issues to deal with. I have both
the knowledge, the test equipment and the machine shop to do this and I know
that for me to make one would cost me several kilobucks in time and
materials. Perhaps you want to share what your smoking.
Steve
I would make the mecanical parts, and
get a counter/photo transistor from www.conrad.com

I dont have to pay myself, you apparently have never
done any hobby work, according to your rules it would
be impossible to make something on the cheap.
The OP wanted something simple/cheap to have some indication
of water consumption, and I dont see where you would
spend all that money on, unless you are trying to
solve a different problem.