Potential scam at gas station near Astrodome.

Was getting food at a food truck in a gas station and a guy comes up to me and says he out of gas and is trying to sell his portable phone charger for money. He tells me he paid $50 for it and I immediately and firmly say no. He continues for a second and I say no again.

Then he goes to the person working the food truck and says the exact same thing, verbatim, except this time he paid $75 for it. They talk for a minute while I wait and he's trying to convince the guy it's fully charged and to plug his phone in.

I finally get my order and he's about to plug his phone into this guy's thing. All the while the guy is trying to sell it for like $50 when it's probably a 10 dollar charger.

Does he want people to plug their phone in and not buy? What's he doing? Seemed really sketchy.