I was also there today and honestly I don't have a CLUE how many ppl were there. With all the dust in the air and not a single helicopter in the sky and everyone spread out over such a large area I can't see how ANYONE, even a news station, could give an accurate number.
I guess that explains why the range is between 100K and 800K. Also, the secular media tends to give lower numbers than the religious media for this kind of thing (R' Ovadia's levaya....).
Could have been over 600K, could have been under. Who knows?