I show 16,685 crystal chips and 1,029,600,192 gold dust to upgrade 644/444 to 777/777 assuming 5250:1 gold to BC exchange rate. The "optimal" CC values per rune level at 5250:1 should be as follows:
level 2 - 31
level 3 - 47
level 4 - 70
level 5 - 105
level 6 - 157
level 7 - 236
I might be wrong though.
PS: Based on 81g per 10,000 gold dust, and 5250g per BC, my method costs 52,137,886.56 gold while the other method costs 72,517,666.34.