This is important because this is specifically referencing mana cost, and not mana value, so you can't fetch a card that has no mana cost (for example: Lotus Bloom) but can fetch cards such as Lion's Eye Diamond, Mox Opal, etc
A few important points: In the US, personal imports under $800 enter duty-free under the de minimis rule
5 Finneas, Ace Archer Tokens And Rabbits Together If you want a more kindred approach, you can always jam Finneas, Ace Archer as your commander
15 Will, Scion Of Peace Negotiations Broke Down If you want to cast spells with a massive mana commitment but want a cheap way to cheat them out, look no further than Will, Scion of Peace
As well as depleting opponents resources, this effect is useful for turning other players best cards over to your side