CS2 trade-up contract basics
A CS2 trade-up contract converts lower-rarity skins into one higher-rarity output. The math is simple at the surface, but the details that decide whether a scenario is worth considering are collection weighting, float output ranges, marketplace fees, and quote freshness.
Input count and rarity movement
Most trade-up contracts use ten inputs from the same rarity tier. The output moves one rarity tier higher and must come from one of the collections represented by the inputs. The special exception is a Covert to Contraband trade-up, which uses five inputs instead of ten.
That input count matters when comparing cost. A contract with cheap individual inputs can still be expensive if the full set is ten skins, and a rare five-input contract can be easier to reason about but harder to source consistently.
Collection weighting
Outputs are not simply split across every possible skin in a flat list. Each input contributes its collection to the pool, and collections with more inputs receive more weight. If five inputs come from one collection and five from another, each collection receives half of the contract weight.
Within a collection, the eligible higher-rarity outputs share that collection's weight. This is why two contracts with the same input cost can have very different expected values: the expensive output may be in a collection that only receives a small portion of the total weight.
Expected value is not guaranteed profit
Expected value is the weighted average value of all possible outputs after accounting for probability and fees. A positive expected value means the long-run average looks favorable under the assumptions used. It does not mean one individual contract is likely to win.
The practical question is whether the expected value is large enough to justify variance, fees, stale listings, marketplace liquidity, and the time needed to source inputs. Thin edges can disappear quickly when a price feed lags or one output has poor demand.
Price source assumptions
Different markets can show different prices for the same skin. A Steam listing floor, a CSFloat listing, and a BUFF buy order are not interchangeable signals. Each one represents a different venue, fee structure, buyer base, and execution path.
When reviewing a trade-up, check whether the input prices are realistically buyable and whether the output prices are realistically sellable. A contract that depends on an old listing or a thin market should be treated as a research lead, not an automatic play.
SkinMerge is an analysis tool. Always verify live marketplace listings, fees, trade holds, and item details before making a purchase or executing a contract.