Explanation

Conditional pricing

A two-reserve pair produces exactly two prices, and both are conditional on the market resolving validly.

What the prices are

The constant-product marginal relationship prices one outcome using the opposite reserve:

conditionalYes = \frac{noReserve}{yesReserve + noReserve}

conditionalNo = \frac{yesReserve}{yesReserve + noReserve}

The two values sum to 100% because they partition the valid outcomes only. That does not imply Invalid has zero probability; there is no unconditional Yes or No probability in this AMM.

At 428.571 Yes and 1,000 No, Conditional Yes is about 70% and Conditional No about 30%. The larger No reserve makes Yes the more expensive side, which is why initializing at 70% Conditional Yes deposits more No than Yes.

Not an oracle

The displayed before-and-after price is a trade-impact aid, nothing more. Reserve spot values can be moved within a block, donated to, sandwiched, or go stale before inclusion. Protocol logic must never consume this price as an oracle; Trading includes no TWAP.