Ending up down three mana on a discard spell to make the trade isnt ideal, but its probably better than any other trade for Esikas Chariot and about the expectation of losing mana against Goldspan Dragon
The key thing to remember is that triggered abilities are not optional in most cases
The fair bucket is the largest, containing cards that are efficient and powerful, but that have a lot of redundancy within the Cube, such as Lightning Bolt, Counterspell, Llanowar Elves, cheap creatures meant for combat, and even big finishers like Frost Titan
Looking at a picture of a Shadowless version and a regular version can help you to see the difference
If youre interested, weve put together a list of great budget cards you can pick up to play in the 99 of a Captain America deck