Mick is well known for mowing the lawn with his kite at 45' or higher, his kite is about level with the horizon, so a guess at 12-14m based on that. The shingle bank is 20ft high, the houses on top are 2 story so around 30ft high so a guess at 50 ft based on that. I am not claiming it any way as i crashed the landing
On a side note I have been thinking of running a boosting comp where you use long lensed cameras fed to a screen that has been marked to more accurately judge boost height.
Imagine a kiter standing still with the kite at 12 at the sea horizon to the left. It is so far away that the kite would be seen at this level (the sea horizon) if it wasn't so far away.
Drawing a horizontal line at this hight shows where another kite standing still at 12, anywhere on the water in the picture, has to be seen in order to jump as high as that kite. Draw a line from "Mick" vertically up to the imaginary line described. Since his kite is fairly right to the side, make an equally long line from Mick towards his kite. Now you can get a good understanding of how high you jumped. Looks roughly like almost half "kite hight" but of course "Mick the lawn mower" may also have very long lines, so it can still be a very, very high jump.
(Even if Mick has short lines I consider the jump in the picture to be very high!)