If someone who presumes to be Jewish is selling gas or generator etc for 2-3 times (or more) the going rate, I seriously question if they are in fact Jewish.
There are 3 main characteristics of Jews:
1. Baishan
2. Rachman
3. Gomel Chasadim
This guy lacks all. He doesn't have busha to do this, he's taking advantage of people in tzarus as opposed to having mercy on them, and he isn't doing a chessed for anone except himself.
More likely an eved or other pisul IMO.
ETA: and whenever I hear these things I ask myself. Do I expect this from someone who doesn't speak English, and is doing this off the back of a truck?
If the answer is yes, then I assume I should stay away.