I wouldn't have thought that frequency is nearly high enough for the sort of 'tricks' you see with tesla coils (the skin effect), no wonder he got a shock... Also, its unlikely to be a neat sine wave as its a blocking oscillator flyback, so the output voltage can be much higher than simply down to the turns ratio (current source output).
I had an old 'electronic' cigarette lighter, I think it was from the 60's or 70's, powered by a small 12V battery (not piezo!) that generated a 1hz arc for igniting the gas - hardly the same as that beast but I was impressed by the ingenuity as it must have been 4-5kv albeit tiny current (pretty much felt like a piezo zap).