How FoilKraken Gets Its Prices and Calculates Box Value

Where do FoilKraken's prices come from?

US prices are TCGplayer market prices, TCGplayer's own estimate from recent completed sales. We collect them once a day through TCGCSV, which republishes TCGplayer's daily price data. Thank you to its maintainer.

European prices come from Cardmarket's public daily price guide. We show Cardmarket's trend price and fall back to its 7- and 30-day averages for thinly traded cards. Cardmarket doesn't say which print a product is (regular, parallel, manga…), so we match its products to TCGplayer's by set, card number and price order: the cheapest print on one market is matched with the cheapest on the other.

To compare the two markets we convert currencies with the European Central Bank's daily reference rate.

How often are prices updated?

Once a day, and every price shows the date it was collected. Card pages keep our own price history from October 21, 2026: we store a new point whenever a price changes, and at least once a week. For One Piece and Gundam cards we also show Cardmarket's 7-day and 30-day averages, which tell you which way prices are moving in Europe right now.

How is a booster box's value calculated?

For each booster set we model what a box contains: how many cards of each rarity it holds, from commons up to manga rares. We value every card at today's market price (the most valuable printing for chase pulls, the regular printing for commons and rares) and count bulk commons and uncommons at 5 cents, because that's what they realistically sell for. Then we open 10,000 virtual boxes with those odds. That gives:

• Average value: what a box returns on average, including the rare big hits.
• Typical box: the median. Half of all boxes do better and half do worse.
• Range: the 10th to 90th percentile, where 8 in 10 boxes land.
• Chance a box beats its price: the share of the 10,000 boxes worth more than the sealed box costs.

The sealed price is the cheapest regular booster box listing for the set. The simulation uses a fixed random seed, so a set's numbers only change when prices change.

What do Open, Lottery and Hold mean?

• Open: the typical box is worth at least what it costs sealed.
• Lottery: the average box is worth its price only because of rare chase cards. Most boxes lose money.
• Hold: opening loses money on average. Keep the box sealed or buy the singles you want.

See today's verdict for every set on Open or Hold.

Where do the pull rates come from?

Bandai doesn't publish pull rates for One Piece, Union Arena or Gundam, so every rate on FoilKraken is an estimate from community case openings and collector data. Each set page lists its sources and a confidence level (low, medium or high). Sets with large case-opening samples are rated higher; older sets and thin data are rated low.

What isn't included?

• Selling costs. Selling pulled cards costs roughly 13% in marketplace fees plus shipping, so real returns are lower than our box values.
• Condition and grading. Prices are for near-mint, ungraded English cards. We don't show PSA, BGS or CGC graded prices, played copies or Japanese cards.
• Union Arena in Europe. Cardmarket doesn't carry Union Arena, so its prices are US only.

How are FoilKraken's pages and guides written?

Card, set and character pages are generated from our price database, so their numbers are always the latest we have. Guides are drafted with AI (Anthropic's Claude) on top of the same database: every number in a guide is filled in from live data when the page loads, and the text is checked against those numbers before it's published. Nothing on FoilKraken is a paid review or a sponsored placement.

Who runs FoilKraken?

FoilKraken is an independent fan site. It isn't affiliated with Bandai, TCGplayer or Cardmarket. Some shop links are affiliate links: if you buy through them we may earn a commission at no extra cost to you. That never changes a price or a verdict.

Found a mistake?

Send us the page link and what looks wrong through our contact page. We check it against the source data and correct it. If a marketplace's own price is wrong, the fix arrives with the next daily update.