Exchange Earth, Moon, and Mars Dollars for Mega Bucks. The price per Mega Buck will increase with each purchase.

Note:

Exchange max per planet: 89 Mega Bucks on Mars, and 91 Mega Bucks on the Earth and Moon.

In Events, you can unlock the exchange once you've collected all of the unlocks. Tap on the Menu (three little lines) > AdVentures > Exchange.