There's no guarantee that you'll have a second target, but in a color combination that's often starved for cards, getting as much value out of each spell is paramount
Premium foil, different artwork, or limited distribution can also make a special uncommon more appealing than its regular version
The default for most Cube designers is that a cube should be singleton, but some favor breaking singleton if the design so requires
Ezuri is one of the best Elf commanders in MTG for players who want a straightforward and effective closer
All of these stack with Inti's ability for tons of card advantage
I cant claim to be such a mastermind as to have picked three mana for my hypothetical for this exact reason, but it is kinda poetic to see that two of the most universal and useful ways to gain incidental life in the format cost three mana at face value