I've had several, almost all of my bikes have been under $100. So my top 10 list:
1. 1980's Redline RL-20 Pro-styler Paid $20
2. Spaceliner frame, fork, crank Paid $30
3. Fuji gran tourer Paid $5
4. '58 Schwinn American and '54 Wasp Paid $8 for both.
5. 1961 and '62 girl's JC Higgins Flightliners Paid $10 for both
6. Tandem trike paid $100 for yellow tandem, traded for light blue tandem and tandem trike then sold the light blue one for $100 to break even so got the trike for FREE!
7. Hawthorne twin top tube Paid $5
8. '66 Schwinn Heavy duty Got on a trade but $5 invested.
9. square tube trike Free
10. The one I find next
And my best Non-bike score
1994 Yamaha Razz Paid $50