one piece card game romance dawn op-01 booster box (OP-01) - Japanese Parallel cards are included as a box topper One Piece Card Game Romance

No other set comes close to this variety at the ultra-rare tier

Collector boosters can also feature Japanese Showcase cards

The Masters Commander sets are scheduled for an August 4, 2023 release, and you can preorder them now

On the other hand, for products like Secret Lair drops, Commander decks, or other preconstructed / box-set supplemental products, we used the cost of buying the sealed product (which is generally lower than the cost of buying all of the cards in the product individually) from around the time the set was released (for sealed product, you'll often pay much more if you wait until the set goes out of print to try to buy it)