ATH = $1242 @ Mt Gox
You cannot count that BS price on Mt Gox when they were ALREADY insolvent and did not payout $$ withdrawals, hence btc price on that exchange was constantly $100 higher since smart people were converting all fiat currencies on MtGox to btc, then withdrawing btc.
It is hard to determine when exactly Mt.Gox become completely insolvent and from which point we should assume Bitcoin's high price was totally caused by their faulty system.
Hence, for the time being - lets accept that $1242 as ATH for future reference.