Saporro was kind of like Arizona. The idea of a pitch that moves, be it on rails or custard, is that it will have to move underneath another structure - the stadium. At saporro the whole stadium was relatively small, maybe 30,000 seats. So the end that the pitch moved under was probably 6,000. And if you look at aerial shots there's no car park or other shit at that end of the ground.
At Spurs one end of the stadium is supported either end of a ~65m hole in the ground, with 17,000 seats above at one end side and a 20 storey office at the other. It's a massive project.