$6, not the one I was thinking of, just the first one I found. Most convenience, Walmart, and similar will have these, and most likely for less as well. Worth taking a look, shipping alone one the parts to build one, would be more than enough to buy one ready built... But then again. some people are willing to pay any price, for the learning experience... Personally, I don't see the point of re-inventing the wheel, unless I can save money, or make some important improvement. Don't know a whole lot about boost converters, but efficiency seems to be a function of the quality of your parts, construction technique, and how well you match up your parts. Might look great on paper, or in simulation, but the final results are usually a little short, or in my case...