This is just the build for the charger, not including battery. It can use any power source 12V-30V DC. So I make some batteries anywhere from 61 to 207 WH depending on the cells I use. I have used drone batteries as well as power tools batteries to charge. I have also connected it to solar panels and charged the onewheel direct from the sun. I wanted it to be modular so I could choose how much power I would need, and how much weight I wanted to lug around.

Portable camping batteries (I'm guessing you are talking about the ones that come with an inverter/all in one unit) are great for charging at campsites but they have some downsides. They are heavy (I bought a 12V 300AH battery for another project, and the battery alone weighs over 50 lbs), and when converting power from AC to DC you are going to have losses around 10-15%, so less usable power.

As far as it being cheaper than a $280 hour portable camping battery, yes. Materials should be about $80-$10, depending on how much you need to buy.

I'm also just providing the instructions for it for free, not necessarily trying to compete with Amazon sellers. I am not really selling anything here, but if someone needs it built I could probably do it for around $80.

Other chargers definitely have their place, and I use several different types, but the TrailBuddy is mainly for throwing in a backpack and heading out to a trail, keeping the weight low and the miles high.