Like most Pokmon cards, the value of Shiftry ex depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Crystal Guardians)
Using Layer Masks is far more practical than using the erase tool on the card scan itself, because theres always a chance to go back
Personally, for as many times as I've sold out of cards and decks, I always keep a deck built around equipment on hand, and a lot of players are the same way
Graded Population Report: Sudowoodo [Reverse Holo] #48 Visualize the distrbution of grades in the chart
Top-loading inserts allow easier access, while side-loading inserts provide a more secure hold
So if you gave an opponent five rad counters, they will mill 10 cards, and there's a chance nine were nonlands, causing more life loss than counters, then a loss of nine rad counters (or all five in this example)