How SkinMerge evaluates CS2 trade-up expected value

1. Start with the complete input cost

The first step is the full contract cost, not the cost of one attractive input. Most trade-ups use ten skins. The Covert to Contraband exception uses five, but those inputs can be harder to source and may have less stable pricing.

Input cost should reflect the market you can actually buy from. A low quote from a venue with stale listings, weak withdrawal support, or limited supply should be treated differently from a current listing or a real buyable order with enough quantity.

2. Weight outputs by collection share

SkinMerge evaluates trade-up probabilities using collection weighting. If six inputs are from one collection and four are from another, the first collection receives 60% of the contract weight and the second receives 40%.

Each collection's weight is then split across its eligible higher-rarity outputs. This means a high-value target can still have a small overall probability when its collection receives little input weight or when that collection has many possible outputs.

3. Map the average float through each output cap

The contract uses the average input float, but each output skin has its own minimum and maximum float range. The output float is normalized through that range, so the same input average can create different wear outcomes across the eligible outputs.

This matters most near wear thresholds. A small float difference can move an output from Minimal Wear to Factory New, or from Field-Tested to Minimal Wear, and that can materially change the sell price used in the expected value calculation.

4. Apply sell-side assumptions to outputs

Output value should be calculated against the venue and fee assumptions you intend to use. A Steam listing floor, a BUFF sell quote, and a direct marketplace quote are not the same thing. They differ in fees, liquidity, withdrawal path, buyer demand, and quote freshness.

SkinMerge exposes source and fee controls because the same contract can move from attractive to unattractive when the output sale route changes. A high expected value based on an output venue you cannot realistically use is not actionable.

5. Separate expected value from risk-adjusted execution

The expected output value is the probability-weighted sum of all eligible outputs after pricing assumptions are applied. Profit is that expected output value minus the total input cost. ROI compares that profit to the capital required for the contract.

Those numbers are long-run averages under the current assumptions. They do not remove variance, trade holds, sourcing difficulty, stale quotes, sudden price movement, or output liquidity. Thin EV edges can disappear before the inputs are purchased.

6. Review freshness and liquidity before acting

Quote age matters because trade-up profitability often depends on small differences between input and output prices. A stale selected-source quote should not be treated as a live buyable or sellable price when ranking candidate contracts.

Liquidity is the second filter. A contract can show a strong calculated margin while depending on an output with few buyers or an input that cannot be bought in enough quantity at the displayed price. Manual marketplace confirmation is part of the workflow.

Practical review checklist

• Confirm every input can be bought at the required float and price.
• Check the complete output distribution, not only the best possible output.
• Verify quote age, venue fees, and sell-route liquidity.
• Account for trade holds, withdrawal rules, currency conversion, and marketplace limits.
• Use custom prices in the builder when your real execution prices differ from the snapshot.