MtG Arena Standard 2020 average XP per game

/*
    output:
    {
        0.50 old:           33.333333333333336,
        0.55 old:           39.032258064516135,
        0.60 old:           45,

        0.50 new:           38,
        0.55 new:           42.56189807774788,
        0.60 new:           47.1638141809291,

        0.50 better new:    38.888888888888886,
        0.55 better new:    43.407629887237846,
        0.60 better new:    47.94212218649518,
    }
*/

const oldOutcomes = {
    ww:  200,
    wl:    0,
    l:     0,
};

const newOutcomes = {
    www:  250,  // 3 wins
    wwlw: 250,
    wlww: 250,
    lwww: 250,

    wwll: 150,  // 2 wins
    wlwl: 150,
    lwwl: 150,

    wll:   50,  // 1 win
    lwl:   50,

    ll:     0,  // 0 wins
};

const betterNewOutcomes = {
    www:  250,  // 3 wins
    wwlw: 250,
    wlww: 250,

    wwll: 150,  // 2 wins
    wlwl: 150,

    wll:   50,  // 1 win

    l:      0,  // 0 wins
};

function averagePrizePerGame (outcomes, winProb) {

    for (const [gameRecord, prize] of Object.entries(outcomes)) {
        let wins = 0;
        let losses = 0;

        for (const g of gameRecord) {
            switch (g) {
                case "w": wins++; break;
                case "l": losses++; break;
                default: throw new Error(`Unknown game result: ${g}`);
            }
        }

        const probability = Math.pow(winProb, wins) * Math.pow(1 - winProb, losses);
        const length = gameRecord.length;
        outcomes[gameRecord] = {prize, probability, length};
    }

    const highestLength = Math.max( ...Object.values(outcomes).map( ({length}) => length ) );

    //     averagePrizePerGame = SUM: probability * (prize + (highestLength - length) * averagePrizePerGame) / highestLength

    //                         =                       SUM: probability * prize / highestLength +
    //                           averagePrizePerGame * SUM: probability * (1 - length / highestLength)

    // <=> (1 - SUM: probability * (1 - length / highestLength)) *  averagePrizePerGame = SUM: probability * prize / highestLength

    // <=> averagePrizePerGame = (  SUM: probability * prize / highestLength  ) / (  1 - SUM: probability * (1 - length / highestLength)  )

    //                         = (  SUM: probability * prize  ) / (  highestLength - SUM: probability * (highestLength - length)  )

    const sum1   = Object.values(outcomes).reduce(
        (acc, {prize, probability, length}) => acc + probability * prize,
        0
    );
    const sum2 = Object.values(outcomes).reduce(
        (acc, {prize, probability, length}) => acc + probability * (highestLength - length),
        0
    );

    return sum1 / (highestLength - sum2);
}

return {
    "0.50 old":        averagePrizePerGame({...oldOutcomes}, 0.5),
    "0.55 old":        averagePrizePerGame({...oldOutcomes}, 0.55),
    "0.60 old":        averagePrizePerGame({...oldOutcomes}, 0.6),
    "0.50 new":        averagePrizePerGame({...newOutcomes}, 0.5),
    "0.55 new":        averagePrizePerGame({...newOutcomes}, 0.55),
    "0.60 new":        averagePrizePerGame({...newOutcomes}, 0.6),
    "0.50 better new": averagePrizePerGame({...betterNewOutcomes}, 0.5),
    "0.55 better new": averagePrizePerGame({...betterNewOutcomes}, 0.55),
    "0.60 better new": averagePrizePerGame({...betterNewOutcomes}, 0.6),
};