The highest possible score for the Legendary Lend a Helping Hand scenario is 103900.
This can be proven as follows:
(1)All scores are multiples of 100.
(2)The largest score you can have on the second-to-last turn is 89900, because if you had any higher the game would end!
(3)The maximum possible income on last turn is 14000 (10 cities plus 4 gold mines occupied by 10 influnce units.)
(4)So 89900 + 14000 = 103900 for the last turn.
This score can be achieved on turn 20. (see picture)
