1.
Mega- is added to nouns that refer to units of measurement in order to form other nouns referring to units that are a million times bigger.
...a 100 megaton explosion.
...a two thousand megawatt surge in electricity.
PREFIX
2.
Mega- combines with nouns and adjectives in order to emphasize the size, quality, or importance of something. (INFORMAL)
Now he can begin to earn the sort of ~bucks he has always dreamed about.
PREFIX emphasis