Funnily enough, it's never really been an important factor in Commander
In the past year, a mint-condition copy of the original Super Mario Bros
This makes it the most expensive Chansey sold to date and is great news for anybody else currently sitting on a mint-condition copy of the card
To determine a spell's total cost, start with the mana cost (or an alternative cost if another card's effect allows you to pay one instead), add any cost increases (such as multikicker), then apply any cost reductions
If you manage to do all four in a single turn, you can also transform Avatar Aang into Aang, Master of Elements a flying creature that reduces spell costs significantly, and lets you transform back for life gain, card draw, counters, and damage