Colorful Cardboard · Evidence
An 11% card gain that was actually a 12.1% drop
A Pokémon card-market article described an approximately 11% gain. The figures for the same part of its hypothetical collection went from $970 to $853. That is a decline of about 12.1%. We could check the discrepancy without predicting where any card price would go next.
The example appeared in Colorful Cardboard’s February market overview, later updated with a June scoreboard. The public page now carries an arithmetic correction dated October 16, 2026. Reading the mistake closely is useful because it separates a wrong calculation from a much harder question: whether a collection has actually made its owner money.
Rebuild the example before trusting the percentage
The article’s table included three Ascended Heroes Elite Trainer Boxes, a Mega Lucario card, a Terapagos card and an Umbreon card. The disputed statement concerned the positions left after excluding Umbreon. Using the rounded figures printed in that table, the boxes went from $354 to $528, Lucario from $316 to $261, and Terapagos from $300 to $64.
Add the starting column: $354 + $316 + $300 = $970. Add the later-value column: $528 + $261 + $64 = $853. The change is the later total minus the starting total: $853 − $970 = −$117.
To express that change as a percentage, divide it by the starting value: −$117 ÷ $970 × 100 = approximately −12.1%. The negative sign is not a matter of interpretation. The later total is lower.
Using $853 as the denominator would answer a different percentage question and produce about −13.7%. Dropping the negative sign would turn a fall into an apparent gain. Neither operation supports the original positive figure. The available record tells us that the stated result was wrong; it does not establish exactly how the original 11% was calculated.
Why exclude Umbreon—and what does that change?
Removing a position can reveal how much a result depends on it, but it also changes the question. It is not a reason to pretend the position never belonged to the original example.
With the displayed Umbreon inputs of $100 and $1,558 added back, the complete table goes from $1,070 to $2,411. Those rounded inputs imply an increase of about 125.3%. The remaining positions, considered separately, show the 12.1% decline. Both calculations can be correct because they describe different baskets.
The comparison shows how heavily the modeled outcome depends on one position. It does not prove that an investor obtained that outcome. In particular, the article’s earlier description of Umbreon at “$100+” does not establish that anyone could or did buy it for exactly $100. A precise calculation cannot repair an uncertain starting assumption.
If you use this method on your own collection, keep the whole-collection result and the smaller comparison clearly labelled. Don’t remove the best or worst card and present the remainder as the performance of the collection you actually held.
Choose a price that describes your card
An entry in a price guide is not automatically a value for the copy in your binder. Start with the set, card number, language, printing and condition. A similarly named card, another version or a different condition can make the comparison misleading before the arithmetic begins.
TCGplayer distinguishes several price points. Its Market Price is based on recent completed sales. Most Recent Sale describes the latest sale for the selected product filters. Listed Median comes from listed asking prices, which can differ substantially from what buyers are paying. The platform’s definitions also specify that selected printings and condition filters affect the displayed data.
That makes the source label part of the number. Record whether you used an asking price, a recent sale or a market estimate, and save the date. If you change that method between two snapshots, explain the change rather than treating it as pure price movement.
Condition deserves a deliberate check. TCGplayer’s standards distinguish Near Mint, Lightly Played, Moderately Played, Heavily Played and Damaged, with examples of the wear and defects that separate them. A card you own should not inherit a Near Mint estimate just because that was the first price you found.
Estimated value, sale proceeds and profit are different amounts
The $970 and $853 figures in the original example were model inputs and later market marks. They were not receipts proving purchases or payments from buyers. A decline between two estimates is not the same evidence as an actual trading loss.
For a real collection, keep the purchase record separate from the valuation record. The first shows what you actually paid, including the relevant acquisition costs you choose to track consistently. The second shows your estimate at a particular time and the evidence used for it. Once a card sells, add the sale record and the direct costs of selling.
Here is an illustrative sale, not a transaction from our records and not a quote for any marketplace’s fee rate. Suppose a collection cost $970, sold for $1,000, incurred $100 in selling fees and cost the seller $20 to ship. The $30 increase over the purchase price disappears once those costs are included: $1,000 − $100 − $20 − $970 = −$90.
If your marketplace statement already shows an after-fee payout, start from that payout and do not subtract the same fee again. Likewise, account for any shipping amount received from the buyer and the actual cost you paid to send the parcel. Use the statement’s breakdown rather than guessing what a single deposit includes. This is a simple cash calculation for the example, not a tax-accounting method.
A collection check you can repeat
For each position, record the exact card or product, quantity, starting amount and what that amount represents. Then record the later amount, source, condition and observation date. Multiply unit prices by quantities before adding the column. A total for three boxes cannot be compared directly with the price of one box.
Use the same positions and quantities in both totals. Purchases or sales made between the dates need separate treatment; otherwise adding new money can look like investment growth. If a price is unavailable, leave it unavailable and explain the gap. Entering zero would describe a worthless card, not missing information.
Finally, label the result according to what you have actually calculated: change in an estimated collection value, gross sale proceeds, or a result after identified costs. For the historical example, the supported answer is an estimated $117 decline in the positions excluding Umbreon. The correction fixes that arithmetic. It does not certify the historical prices or turn the hypothetical collection into anyone’s realised trading history.
Original market overview and its arithmetic correction