I wanted a bike that few people would invest the effort in stealing. It's a Raleigh M-30 that I bought at a pawn shop for $30. Most of the additions have been free or cheap enough to keep the total investment under $35.
The handlebars were off a discarded little girl's bike. The grips are off a discarded wheelchair. The seat was given to me by a friend when she replaced the seat on her Trek mtb. It is chained down with a bike chain. The fenders are off an old Armstrong. The rear rack was on clearance at Toys R Us for
$1.62. The basket is an old high school gym locker basket. I did put on two Planet Bike Superflash blinkies, and a Planet Bike Beamer headlight. Those cost as much as the bike, but I can take them with me.
The lock is a Kryptonite New York Noose. $70 of lock for $30 of bike. That ought to keep the thieves disinterested.
Then I spent $90 on tires and blew my budget. Cest le' vie.