The real economics of CS2 trade-up contracts

A trade-up contract takes 10 skins of the same rarity and the same side (CT/T/either) and produces one skin one rarity above. The float of the output is a weighted average of the inputs. The specific output skin is randomly drawn from the union of all possible higher-rarity skins from collections represented in your inputs.

That last sentence is the entire game. The randomness is bounded —you control which collections appear in your inputs, and you control how many slots each collection gets. Get the math right and trade-ups are a positive-expected-value arbitrage with bounded downside. Get it wrong and you are donating to the in-game economy.

The mechanic, in detail

• Same rarity across all 10 inputs (Consumer, Industrial, Mil-Spec, Restricted, Classified).
• Same side — either all CT, all T, or all can be used by both. Cannot mix.
• Output rarity = input rarity + 1. Covert trade-ups exist but produce... another covert (no “knife tier” from trade-ups).
• Output float = average of input floats, rescaled to the output skin’s wear range. Lower input floats mean lower output float, generally.
• Output skin = randomly drawn from the set of all higher-rarity skins in the union of input collections. If 6/10 of your inputs are from Collection A and 4/10 from Collection B, your probability is 60% A higher-tier, 40% B higher-tier —then uniform within whichever collection wins.

That last rule is the key strategic lever. If Collection A has 4 higher-rarity skins worth €5, €6, €8, and €40, and Collection B has 3 skins worth €15, €18, €22, you can deliberately weight your contract toward whichever collection has the best expected value.

The expected-value formula

Expected output value (before fees) =

EV = ∑collection P(collection) * ∑skin in higher-rarity(1 / Nskins) * price(skin)

Where P(collection) = (slots from that collection) / 10.

Subtract: total input cost + ~€0 contract fee (trade-ups themselves are free, but you pay seller fee when you eventually sell the output).

Subtract again: variance discount. A trade-up with a 5% chance of producing a €200 skin and 95% chance of producing a €3 skin has the same EV as one that always produces a €13 skin, but the variance is wildly different. For most traders, predictable matters.

A worked example

Goal: a Restricted trade-up using mil-spec inputs that yields StatTrak Five-SeveN | Hyper Beast or similar mid-rarity output.

Pick 10 inputs all from one collection — say, all from The Chroma 3 Collection. That collection has 5 Restricted skins. After the contract, output is uniformly random across those 5.

EV = (6.50 + 4.20 + 5.10 + 28.40 + 14.20) / 5 = €11.68.

Net of 12% Skinport seller fee: €10.28.

If you can source the 10 mil-spec Chroma 3 inputs for less than €1.02 each (€10.20 total), the trade-up is +EV. In practice mil-spec Chroma 3 floats around €0.80—€1.30 depending on float and StatTrak status, so this is on the edge.

Float scaling is where the real edge is

The output’s wear is determined by the weighted-average float of the inputs, rescaled to the output skin’s wear range. Important: a skin’s wear range is not always 0.00—1.00. Many skins are float-capped to, say, 0.00—0.50 (no Well-Worn or Battle-Scarred exists).

So if you stuff 10 inputs at 0.06 each (Factory New territory), you’ll average 0.06 and the output gets rescaled into FN of its own range. That output’s FN sells for a meaningful premium over its FT.

Strategy: buy the cheapest low-float input listings (often the cheapest are not low-float at all because volume sellers don’t differentiate). You’re betting the float-premium-on-output more than covers the float-premium-on-inputs.

When trade-ups beat raw flipping

• Single-collection contracts where one specific output is meaningfully more valuable than the others and you can’t buy that target cheaper directly.
• Float-multiplier plays where input FN is cheap and output FN of the high-value skin sells at a 3—5x multiplier of its FT.
• Collections with a stuck supply. If a target skin has 200 listings on Skinport but a thin order book, you may be able to absorb cheap floor inputs and produce supply on a venue with deeper buyers.

When to skip the trade-up

• If you can’t articulate the EV in your head before clicking, skip.
• If variance scares you and the EV edge is below 10%, skip.
• If the cheapest input listing has a 7-day Steam trade hold and you’re paying with sale-funded balance you need this week, skip.
• If the target skin’s liquidity is Tier D or E, skip — you may produce a skin you can’t sell at the EV price.

Trade-ups are not free upgrades or casino plays. They are arbitrage on the float-and-collection mechanics, and like all arbitrage they only work when you’ve done the math before you click the button. SkinScope’s Trade-Up scanner lists active +EV contracts using current cross-venue prices, but every flagged play deserves a manual sanity check.