Design should never begin with lowering costs of material put on the board, reality is that ‘free material’ is a sign for having a lack of any honest creativity. In fact so called ‘free material’ leads to not only an ‘Arms Race’ for material advantage it closes up design spaces where more interesting development could have occurred, but is unable to be achieved due to speedy unimaginative decks.
Inventive features do something never seen before, that have synergy, although it must interact with a fairness not overpower other progresses. Once the freeness begins it convolutes the game’s design space forever, in that you need to keep developing this free material more and more. Consider Infantry Carrier (packs many free units), Madness (too OP, turns many games over), Typhoon (free mass multi-damage) these new designs only keep up with the Arms Race of ‘too much low cost silliness’ that is already allowed. MTG moxes and Black Lotus was a learning curve for WOTC, learn from other designer mistakes, do not repeat them.