How much should one spend on a bicycle?

I know that a lot of details would factor into this, but I am
wondering what bicycle enthusiasts consider when buying a new (or
used) bike?

I guess I don't want to underspend and end up w/ a piece of cra*, but
I also don't want to overspend and risk having it get stolen.

I would like to use it for daily exercise and going to the store (not
more than 10 miles one way).