I used old Northworst Frequent Flyer Miles, so......
Airfare to San Francisco $0.00
3 Nights at USA Hostels Downtown San Fran $75.00
BART & CAL TRAN fares $35.00
Maker Faire Weekend Pass $30.00
Hanging out with 60,000+ geeks like myself for two great days of fun and idea sharing...... Priceless
food and drink for the weekend will most likely end up being more than the $140 above...