As of this writing (updated January 1, 2014), there are two Chinese bus companies that charge $12 to $30 for a one-way ticket between NYC and Boston:
Popular competitor Fung Wah Bus has been shut down since March 2013 by the US Federal Motor Carrier Safety Administration.
Bear in mind, we're not talking about luxury transportation here. If you're seeking a comfy ride and many amenities en route, you may prefer to take the LimoLiner between Boston and New York. However, if you're a college student or other traveler with limited means, you'll be among frugal comrades in addition to many Chinese travelers.
Several other bus companies are affordable alternatives to riding the Chinese bus from NYC to Boston. It's worthwhile to compare rates from these bus services: