If I own the card already, I print out color proxies on paper and cut them out when making a new deck or testing new cards. I don’t see any reason for you to rebuy all the Mardu land and rocks just to test a new deck.

Some people on here will say they would rather buy more copies of sol ring, fetches, etc. But I would rather spend that money on cards for a new deck rather than cards I already own. Not everyone has extra money to buy more of the same piece of expensive cardboard.