For example, if you cast Junkblade Bruiser (a creature with a mana value of 5 and an ability that triggers whenever you expend 4) by paying its full cost of five mana, you'll already have spent four mana on spells before Junkblade Bruiser enters, and therefore its ability that triggers whenever you expend 4 won't be able to trigger at all that turn.
This Duskmourn Commander is one of the strongest cost reducers in the game, even if you're restricted to the first enchantment you draw in a turn, and is very flexible: Aminatou, Veil Piercer EDH decks can be built in lots of different ways
Since the pandemic and the pro scenes near-implosion, those once-iconic staples have lost much of their value, while cards for Commander, a casual format played on kitchen tables, shot up
But most of the time it is 2 for 1 at maximum, so I usually dont use them
Path to Exile ($9) Another mega-staple, we can see that the Fallout version is now over $20 and that one doesnt even have Tidus on it