no 50x. If you design your applications correctly with the right data structures, you rarely need all the computational power today´s machines have. In some cases, yea probably. but in most cases, hardware is already too good!
Well it seems like the clock example they have can't even hit 60 FPS without consuming 100% cpu (of one core). So yeah you probably don't want to actually use Python in the browser (via a JS interpreter).
Is that a typo? Did you mean "50%"?