I came to a similar conclusion on my own
However, simply put, I believe the 780 to be a red herring and only exists to get participants thinking.
There is a combination of 30 randomly generated numbers taken from the 26 English characters. 30x26=780.
What if we managed to create a basic cipher using the algorithms the game runs off? It appears as though each letter might have a designated value between 1 and 26. It would then be possible to reach 780 if the sequence was completely occupied by the character that represents 26, but that wouldn't be the purpose of course. This new cipher could be used to decrypt other messages within the puzzle.
Alternatively, it might also be the case that the value of each letter goes up dependant on it's relation to its placement within the sequence. For example, if in the correct position, 'A' might have a value of 26 in the first position but only a 18 in the second position. If that were the case then the goal of 780 would be achieved by correctly completing the sequence and possibly creating a phrase or word.
I'm pretty freakin' tired and I hope this is legible. "Food for thought" anyway.