I would assume gasoline Charlie. These have been around for quite some time (I remember drooling over smaller versions when I was a kid), but I've never seen video of one. Better know what you are doing! I'd hate to crash that sucker!
It's a true turbine jet engine RC plane. They also make what are called "inducted fan" jets. Apparently the ones like in the video take quite a bit of skill to handle....mainly in landing! lol.
Should give you an idea...
My guess on the one in the picture? $25K
Oh yeah, and it sounds like you have to have a waiver from the association that controls RC airplanes just to fly these things at any of their locations (airstrips). I'm sure if you can afford the thing you can find somewhere to fly it outside of their purview, but only about .5% of their members have the waiver to fly these things.