Slim and naked, the Harley Softail Street Bob offers just the basics, and is available only with the Milwaukee-Eight 107 engine, which is more than enough for a spirited rip around town. 3.5 gal. The price of the Harley Street Bob 107 is $14,549 for the Vivid Black version, with color options costing $14,949, and two-tone prices at $15,299.